Add m-esr52 at 52.6.0

1 files changed, 9186 insertions, 0 deletions

diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
new file mode 100644
index 000000000..ed34f39ce
--- /dev/null
+++ b/layout/base/nsLayoutUtils.cpp
@@ -0,0 +1,9186 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 sw=2 et tw=78: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsLayoutUtils.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/BasicEvents.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/EffectCompositor.h"
+#include "mozilla/EffectSet.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/gfx/gfxVars.h"
+#include "mozilla/gfx/PathHelpers.h"
+#include "mozilla/layers/PAPZ.h"
+#include "mozilla/Likely.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/Unused.h"
+#include "nsCharTraits.h"
+#include "nsFontMetrics.h"
+#include "nsPresContext.h"
+#include "nsIContent.h"
+#include "nsIDOMHTMLDocument.h"
+#include "nsIDOMHTMLElement.h"
+#include "nsFrameList.h"
+#include "nsGkAtoms.h"
+#include "nsHtml5Atoms.h"
+#include "nsIAtom.h"
+#include "nsCaret.h"
+#include "nsCSSPseudoElements.h"
+#include "nsCSSAnonBoxes.h"
+#include "nsCSSColorUtils.h"
+#include "nsView.h"
+#include "nsViewManager.h"
+#include "nsPlaceholderFrame.h"
+#include "nsIScrollableFrame.h"
+#include "nsIDOMEvent.h"
+#include "nsDisplayList.h"
+#include "nsRegion.h"
+#include "nsFrameManager.h"
+#include "nsBlockFrame.h"
+#include "nsBidiPresUtils.h"
+#include "imgIContainer.h"
+#include "ImageOps.h"
+#include "ImageRegion.h"
+#include "gfxRect.h"
+#include "gfxContext.h"
+#include "nsRenderingContext.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsCSSRendering.h"
+#include "nsTextFragment.h"
+#include "nsThemeConstants.h"
+#include "nsPIDOMWindow.h"
+#include "nsIDocShell.h"
+#include "nsIWidget.h"
+#include "gfxMatrix.h"
+#include "gfxPrefs.h"
+#include "gfxTypes.h"
+#include "nsTArray.h"
+#include "mozilla/dom/HTMLCanvasElement.h"
+#include "nsICanvasRenderingContextInternal.h"
+#include "gfxPlatform.h"
+#include <algorithm>
+#include <limits>
+#include "mozilla/dom/HTMLVideoElement.h"
+#include "mozilla/dom/HTMLImageElement.h"
+#include "mozilla/dom/DOMRect.h"
+#include "mozilla/dom/DOMStringList.h"
+#include "mozilla/dom/KeyframeEffectReadOnly.h"
+#include "mozilla/layers/APZCCallbackHelper.h"
+#include "imgIRequest.h"
+#include "nsIImageLoadingContent.h"
+#include "nsCOMPtr.h"
+#include "nsCSSProps.h"
+#include "nsListControlFrame.h"
+#include "mozilla/dom/Element.h"
+#include "nsCanvasFrame.h"
+#include "gfxDrawable.h"
+#include "gfxEnv.h"
+#include "gfxUtils.h"
+#include "nsDataHashtable.h"
+#include "nsTableWrapperFrame.h"
+#include "nsTextFrame.h"
+#include "nsFontFaceList.h"
+#include "nsFontInflationData.h"
+#include "nsSVGUtils.h"
+#include "SVGImageContext.h"
+#include "SVGTextFrame.h"
+#include "nsStyleStructInlines.h"
+#include "nsStyleTransformMatrix.h"
+#include "nsIFrameInlines.h"
+#include "ImageContainer.h"
+#include "nsComputedDOMStyle.h"
+#include "ActiveLayerTracker.h"
+#include "mozilla/gfx/2D.h"
+#include "gfx2DGlue.h"
+#include "mozilla/LookAndFeel.h"
+#include "UnitTransforms.h"
+#include "TiledLayerBuffer.h" // For TILEDLAYERBUFFER_TILE_SIZE
+#include "ClientLayerManager.h"
+#include "nsRefreshDriver.h"
+#include "nsIContentViewer.h"
+#include "LayersLogging.h"
+#include "mozilla/Preferences.h"
+#include "nsFrameSelection.h"
+#include "FrameLayerBuilder.h"
+#include "mozilla/layers/APZCTreeManager.h"
+#include "mozilla/layers/CompositorBridgeChild.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/EventStateManager.h"
+#include "mozilla/RuleNodeCacheConditions.h"
+#include "mozilla/StyleSetHandle.h"
+#include "mozilla/StyleSetHandleInlines.h"
+#include "RegionBuilder.h"
+
+#ifdef MOZ_XUL
+#include "nsXULPopupManager.h"
+#endif
+
+#include "GeckoProfiler.h"
+#include "nsAnimationManager.h"
+#include "nsTransitionManager.h"
+#include "mozilla/RestyleManagerHandle.h"
+#include "mozilla/RestyleManagerHandleInlines.h"
+#include "LayoutLogging.h"
+
+// Make sure getpid() works.
+#ifdef XP_WIN
+#include <process.h>
+#define getpid _getpid
+#else
+#include <unistd.h>
+#endif
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::image;
+using namespace mozilla::layers;
+using namespace mozilla::layout;
+using namespace mozilla::gfx;
+
+#define GRID_ENABLED_PREF_NAME "layout.css.grid.enabled"
+#define GRID_TEMPLATE_SUBGRID_ENABLED_PREF_NAME "layout.css.grid-template-subgrid-value.enabled"
+#define WEBKIT_PREFIXES_ENABLED_PREF_NAME "layout.css.prefixes.webkit"
+#define DISPLAY_CONTENTS_ENABLED_PREF_NAME "layout.css.display-contents.enabled"
+#define TEXT_ALIGN_UNSAFE_ENABLED_PREF_NAME "layout.css.text-align-unsafe-value.enabled"
+#define FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME "layout.css.float-logical-values.enabled"
+#define BG_CLIP_TEXT_ENABLED_PREF_NAME "layout.css.background-clip-text.enabled"
+
+// The time in number of frames that we estimate for a refresh driver
+// to be quiescent
+#define DEFAULT_QUIESCENT_FRAMES 2
+// The time (milliseconds) we estimate is needed between the end of an
+// idle time and the next Tick.
+#define DEFAULT_IDLE_PERIOD_TIME_LIMIT 1.0f
+
+#ifdef DEBUG
+// TODO: remove, see bug 598468.
+bool nsLayoutUtils::gPreventAssertInCompareTreePosition = false;
+#endif // DEBUG
+
+typedef FrameMetrics::ViewID ViewID;
+typedef nsStyleTransformMatrix::TransformReferenceBox TransformReferenceBox;
+
+/* static */ uint32_t nsLayoutUtils::sFontSizeInflationEmPerLine;
+/* static */ uint32_t nsLayoutUtils::sFontSizeInflationMinTwips;
+/* static */ uint32_t nsLayoutUtils::sFontSizeInflationLineThreshold;
+/* static */ int32_t  nsLayoutUtils::sFontSizeInflationMappingIntercept;
+/* static */ uint32_t nsLayoutUtils::sFontSizeInflationMaxRatio;
+/* static */ bool nsLayoutUtils::sFontSizeInflationForceEnabled;
+/* static */ bool nsLayoutUtils::sFontSizeInflationDisabledInMasterProcess;
+/* static */ bool nsLayoutUtils::sInvalidationDebuggingIsEnabled;
+/* static */ bool nsLayoutUtils::sCSSVariablesEnabled;
+/* static */ bool nsLayoutUtils::sInterruptibleReflowEnabled;
+/* static */ bool nsLayoutUtils::sSVGTransformBoxEnabled;
+/* static */ bool nsLayoutUtils::sTextCombineUprightDigitsEnabled;
+#ifdef MOZ_STYLO
+/* static */ bool nsLayoutUtils::sStyloEnabled;
+#endif
+/* static */ uint32_t nsLayoutUtils::sIdlePeriodDeadlineLimit;
+/* static */ uint32_t nsLayoutUtils::sQuiescentFramesBeforeIdlePeriod;
+
+static ViewID sScrollIdCounter = FrameMetrics::START_SCROLL_ID;
+
+typedef nsDataHashtable<nsUint64HashKey, nsIContent*> ContentMap;
+static ContentMap* sContentMap = nullptr;
+static ContentMap& GetContentMap() {
+  if (!sContentMap) {
+    sContentMap = new ContentMap();
+  }
+  return *sContentMap;
+}
+
+// When the pref "layout.css.grid.enabled" changes, this function is invoked
+// to let us update kDisplayKTable, to selectively disable or restore the
+// entries for "grid" and "inline-grid" in that table.
+static void
+GridEnabledPrefChangeCallback(const char* aPrefName, void* aClosure)
+{
+  MOZ_ASSERT(strncmp(aPrefName, GRID_ENABLED_PREF_NAME,
+                     ArrayLength(GRID_ENABLED_PREF_NAME)) == 0,
+             "We only registered this callback for a single pref, so it "
+             "should only be called for that pref");
+
+  static int32_t sIndexOfGridInDisplayTable;
+  static int32_t sIndexOfInlineGridInDisplayTable;
+  static bool sAreGridKeywordIndicesInitialized; // initialized to false
+
+  bool isGridEnabled =
+    Preferences::GetBool(GRID_ENABLED_PREF_NAME, false);
+  if (!sAreGridKeywordIndicesInitialized) {
+    // First run: find the position of "grid" and "inline-grid" in
+    // kDisplayKTable.
+    sIndexOfGridInDisplayTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_grid,
+                                     nsCSSProps::kDisplayKTable);
+    MOZ_ASSERT(sIndexOfGridInDisplayTable >= 0,
+               "Couldn't find grid in kDisplayKTable");
+    sIndexOfInlineGridInDisplayTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_inline_grid,
+                                     nsCSSProps::kDisplayKTable);
+    MOZ_ASSERT(sIndexOfInlineGridInDisplayTable >= 0,
+               "Couldn't find inline-grid in kDisplayKTable");
+    sAreGridKeywordIndicesInitialized = true;
+  }
+
+  // OK -- now, stomp on or restore the "grid" entries in kDisplayKTable,
+  // depending on whether the grid pref is enabled vs. disabled.
+  if (sIndexOfGridInDisplayTable >= 0) {
+    nsCSSProps::kDisplayKTable[sIndexOfGridInDisplayTable].mKeyword =
+      isGridEnabled ? eCSSKeyword_grid : eCSSKeyword_UNKNOWN;
+  }
+  if (sIndexOfInlineGridInDisplayTable >= 0) {
+    nsCSSProps::kDisplayKTable[sIndexOfInlineGridInDisplayTable].mKeyword =
+      isGridEnabled ? eCSSKeyword_inline_grid : eCSSKeyword_UNKNOWN;
+  }
+}
+
+// When the pref "layout.css.prefixes.webkit" changes, this function is invoked
+// to let us update kDisplayKTable, to selectively disable or restore the
+// entries for "-webkit-box" and "-webkit-inline-box" in that table.
+static void
+WebkitPrefixEnabledPrefChangeCallback(const char* aPrefName, void* aClosure)
+{
+  MOZ_ASSERT(strncmp(aPrefName, WEBKIT_PREFIXES_ENABLED_PREF_NAME,
+                     ArrayLength(WEBKIT_PREFIXES_ENABLED_PREF_NAME)) == 0,
+             "We only registered this callback for a single pref, so it "
+             "should only be called for that pref");
+
+  static int32_t sIndexOfWebkitBoxInDisplayTable;
+  static int32_t sIndexOfWebkitInlineBoxInDisplayTable;
+  static int32_t sIndexOfWebkitFlexInDisplayTable;
+  static int32_t sIndexOfWebkitInlineFlexInDisplayTable;
+
+  static bool sAreKeywordIndicesInitialized; // initialized to false
+
+  bool isWebkitPrefixSupportEnabled =
+    Preferences::GetBool(WEBKIT_PREFIXES_ENABLED_PREF_NAME, false);
+  if (!sAreKeywordIndicesInitialized) {
+    // First run: find the position of the keywords in kDisplayKTable.
+    sIndexOfWebkitBoxInDisplayTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword__webkit_box,
+                                     nsCSSProps::kDisplayKTable);
+    MOZ_ASSERT(sIndexOfWebkitBoxInDisplayTable >= 0,
+               "Couldn't find -webkit-box in kDisplayKTable");
+    sIndexOfWebkitInlineBoxInDisplayTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword__webkit_inline_box,
+                                     nsCSSProps::kDisplayKTable);
+    MOZ_ASSERT(sIndexOfWebkitInlineBoxInDisplayTable >= 0,
+               "Couldn't find -webkit-inline-box in kDisplayKTable");
+
+    sIndexOfWebkitFlexInDisplayTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword__webkit_flex,
+                                     nsCSSProps::kDisplayKTable);
+    MOZ_ASSERT(sIndexOfWebkitFlexInDisplayTable >= 0,
+               "Couldn't find -webkit-flex in kDisplayKTable");
+    sIndexOfWebkitInlineFlexInDisplayTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword__webkit_inline_flex,
+                                     nsCSSProps::kDisplayKTable);
+    MOZ_ASSERT(sIndexOfWebkitInlineFlexInDisplayTable >= 0,
+               "Couldn't find -webkit-inline-flex in kDisplayKTable");
+    sAreKeywordIndicesInitialized = true;
+  }
+
+  // OK -- now, stomp on or restore the "-webkit-{box|flex}" entries in
+  // kDisplayKTable, depending on whether the webkit prefix pref is enabled
+  // vs. disabled.
+  if (sIndexOfWebkitBoxInDisplayTable >= 0) {
+    nsCSSProps::kDisplayKTable[sIndexOfWebkitBoxInDisplayTable].mKeyword =
+      isWebkitPrefixSupportEnabled ?
+      eCSSKeyword__webkit_box : eCSSKeyword_UNKNOWN;
+  }
+  if (sIndexOfWebkitInlineBoxInDisplayTable >= 0) {
+    nsCSSProps::kDisplayKTable[sIndexOfWebkitInlineBoxInDisplayTable].mKeyword =
+      isWebkitPrefixSupportEnabled ?
+      eCSSKeyword__webkit_inline_box : eCSSKeyword_UNKNOWN;
+  }
+  if (sIndexOfWebkitFlexInDisplayTable >= 0) {
+    nsCSSProps::kDisplayKTable[sIndexOfWebkitFlexInDisplayTable].mKeyword =
+      isWebkitPrefixSupportEnabled ?
+      eCSSKeyword__webkit_flex : eCSSKeyword_UNKNOWN;
+  }
+  if (sIndexOfWebkitInlineFlexInDisplayTable >= 0) {
+    nsCSSProps::kDisplayKTable[sIndexOfWebkitInlineFlexInDisplayTable].mKeyword =
+      isWebkitPrefixSupportEnabled ?
+      eCSSKeyword__webkit_inline_flex : eCSSKeyword_UNKNOWN;
+  }
+}
+
+// When the pref "layout.css.display-contents.enabled" changes, this function is
+// invoked to let us update kDisplayKTable, to selectively disable or restore
+// the entries for "contents" in that table.
+static void
+DisplayContentsEnabledPrefChangeCallback(const char* aPrefName, void* aClosure)
+{
+  NS_ASSERTION(strcmp(aPrefName, DISPLAY_CONTENTS_ENABLED_PREF_NAME) == 0,
+               "Did you misspell " DISPLAY_CONTENTS_ENABLED_PREF_NAME " ?");
+
+  static bool sIsDisplayContentsKeywordIndexInitialized;
+  static int32_t sIndexOfContentsInDisplayTable;
+  bool isDisplayContentsEnabled =
+    Preferences::GetBool(DISPLAY_CONTENTS_ENABLED_PREF_NAME, false);
+
+  if (!sIsDisplayContentsKeywordIndexInitialized) {
+    // First run: find the position of "contents" in kDisplayKTable.
+    sIndexOfContentsInDisplayTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_contents,
+                                     nsCSSProps::kDisplayKTable);
+    sIsDisplayContentsKeywordIndexInitialized = true;
+  }
+
+  // OK -- now, stomp on or restore the "contents" entry in kDisplayKTable,
+  // depending on whether the pref is enabled vs. disabled.
+  if (sIndexOfContentsInDisplayTable >= 0) {
+    nsCSSProps::kDisplayKTable[sIndexOfContentsInDisplayTable].mKeyword =
+      isDisplayContentsEnabled ? eCSSKeyword_contents : eCSSKeyword_UNKNOWN;
+  }
+}
+
+// When the pref "layout.css.text-align-unsafe-value.enabled" changes, this
+// function is called to let us update kTextAlignKTable & kTextAlignLastKTable,
+// to selectively disable or restore the entries for "unsafe" in those tables.
+static void
+TextAlignUnsafeEnabledPrefChangeCallback(const char* aPrefName, void* aClosure)
+{
+  NS_ASSERTION(strcmp(aPrefName, TEXT_ALIGN_UNSAFE_ENABLED_PREF_NAME) == 0,
+               "Did you misspell " TEXT_ALIGN_UNSAFE_ENABLED_PREF_NAME " ?");
+
+  static bool sIsInitialized;
+  static int32_t sIndexOfUnsafeInTextAlignTable;
+  static int32_t sIndexOfUnsafeInTextAlignLastTable;
+  bool isTextAlignUnsafeEnabled =
+    Preferences::GetBool(TEXT_ALIGN_UNSAFE_ENABLED_PREF_NAME, false);
+
+  if (!sIsInitialized) {
+    // First run: find the position of "unsafe" in kTextAlignKTable.
+    sIndexOfUnsafeInTextAlignTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_unsafe,
+                                     nsCSSProps::kTextAlignKTable);
+    // First run: find the position of "unsafe" in kTextAlignLastKTable.
+    sIndexOfUnsafeInTextAlignLastTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_unsafe,
+                                     nsCSSProps::kTextAlignLastKTable);
+    sIsInitialized = true;
+  }
+
+  // OK -- now, stomp on or restore the "unsafe" entry in the keyword tables,
+  // depending on whether the pref is enabled vs. disabled.
+  MOZ_ASSERT(sIndexOfUnsafeInTextAlignTable >= 0);
+  nsCSSProps::kTextAlignKTable[sIndexOfUnsafeInTextAlignTable].mKeyword =
+    isTextAlignUnsafeEnabled ? eCSSKeyword_unsafe : eCSSKeyword_UNKNOWN;
+  MOZ_ASSERT(sIndexOfUnsafeInTextAlignLastTable >= 0);
+  nsCSSProps::kTextAlignLastKTable[sIndexOfUnsafeInTextAlignLastTable].mKeyword =
+    isTextAlignUnsafeEnabled ? eCSSKeyword_unsafe : eCSSKeyword_UNKNOWN;
+}
+
+// When the pref "layout.css.float-logical-values.enabled" changes, this
+// function is called to let us update kFloatKTable & kClearKTable,
+// to selectively disable or restore the entries for logical values
+// (inline-start and inline-end) in those tables.
+static void
+FloatLogicalValuesEnabledPrefChangeCallback(const char* aPrefName,
+                                            void* aClosure)
+{
+  NS_ASSERTION(strcmp(aPrefName, FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME) == 0,
+               "Did you misspell " FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME " ?");
+
+  static bool sIsInitialized;
+  static int32_t sIndexOfInlineStartInFloatTable;
+  static int32_t sIndexOfInlineEndInFloatTable;
+  static int32_t sIndexOfInlineStartInClearTable;
+  static int32_t sIndexOfInlineEndInClearTable;
+  bool isFloatLogicalValuesEnabled =
+    Preferences::GetBool(FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME, false);
+
+  if (!sIsInitialized) {
+    // First run: find the position of "inline-start" in kFloatKTable.
+    sIndexOfInlineStartInFloatTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_inline_start,
+                                     nsCSSProps::kFloatKTable);
+    // First run: find the position of "inline-end" in kFloatKTable.
+    sIndexOfInlineEndInFloatTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_inline_end,
+                                     nsCSSProps::kFloatKTable);
+    // First run: find the position of "inline-start" in kClearKTable.
+    sIndexOfInlineStartInClearTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_inline_start,
+                                     nsCSSProps::kClearKTable);
+    // First run: find the position of "inline-end" in kClearKTable.
+    sIndexOfInlineEndInClearTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_inline_end,
+                                     nsCSSProps::kClearKTable);
+    sIsInitialized = true;
+  }
+
+  // OK -- now, stomp on or restore the logical entries in the keyword tables,
+  // depending on whether the pref is enabled vs. disabled.
+  MOZ_ASSERT(sIndexOfInlineStartInFloatTable >= 0);
+  nsCSSProps::kFloatKTable[sIndexOfInlineStartInFloatTable].mKeyword =
+    isFloatLogicalValuesEnabled ? eCSSKeyword_inline_start : eCSSKeyword_UNKNOWN;
+  MOZ_ASSERT(sIndexOfInlineEndInFloatTable >= 0);
+  nsCSSProps::kFloatKTable[sIndexOfInlineEndInFloatTable].mKeyword =
+    isFloatLogicalValuesEnabled ? eCSSKeyword_inline_end : eCSSKeyword_UNKNOWN;
+  MOZ_ASSERT(sIndexOfInlineStartInClearTable >= 0);
+  nsCSSProps::kClearKTable[sIndexOfInlineStartInClearTable].mKeyword =
+    isFloatLogicalValuesEnabled ? eCSSKeyword_inline_start : eCSSKeyword_UNKNOWN;
+  MOZ_ASSERT(sIndexOfInlineEndInClearTable >= 0);
+  nsCSSProps::kClearKTable[sIndexOfInlineEndInClearTable].mKeyword =
+    isFloatLogicalValuesEnabled ? eCSSKeyword_inline_end : eCSSKeyword_UNKNOWN;
+}
+
+
+// When the pref "layout.css.background-clip-text.enabled" changes, this
+// function is invoked to let us update kBackgroundClipKTable, to selectively
+// disable or restore the entries for "text" in that table.
+static void
+BackgroundClipTextEnabledPrefChangeCallback(const char* aPrefName,
+                                            void* aClosure)
+{
+  NS_ASSERTION(strcmp(aPrefName, BG_CLIP_TEXT_ENABLED_PREF_NAME) == 0,
+               "Did you misspell " BG_CLIP_TEXT_ENABLED_PREF_NAME " ?");
+
+  static bool sIsBGClipKeywordIndexInitialized;
+  static int32_t sIndexOfTextInBGClipTable;
+  bool isBGClipTextEnabled =
+    Preferences::GetBool(BG_CLIP_TEXT_ENABLED_PREF_NAME, false);
+
+  if (!sIsBGClipKeywordIndexInitialized) {
+    // First run: find the position of "text" in kBackgroundClipKTable.
+    sIndexOfTextInBGClipTable =
+      nsCSSProps::FindIndexOfKeyword(eCSSKeyword_text,
+                                     nsCSSProps::kBackgroundClipKTable);
+
+    sIsBGClipKeywordIndexInitialized = true;
+  }
+
+  // OK -- now, stomp on or restore the "text" entry in kBackgroundClipKTable,
+  // depending on whether the pref is enabled vs. disabled.
+  if (sIndexOfTextInBGClipTable >= 0) {
+    nsCSSProps::kBackgroundClipKTable[sIndexOfTextInBGClipTable].mKeyword =
+      isBGClipTextEnabled ? eCSSKeyword_text : eCSSKeyword_UNKNOWN;
+  }
+}
+
+template<typename TestType>
+static bool
+HasMatchingAnimations(const nsIFrame* aFrame, TestType&& aTest)
+{
+  EffectSet* effects = EffectSet::GetEffectSet(aFrame);
+  if (!effects) {
+    return false;
+  }
+
+  for (KeyframeEffectReadOnly* effect : *effects) {
+    if (aTest(*effect)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool
+nsLayoutUtils::HasCurrentTransitions(const nsIFrame* aFrame)
+{
+  return HasMatchingAnimations(aFrame,
+    [](KeyframeEffectReadOnly& aEffect)
+    {
+      // Since |aEffect| is current, it must have an associated Animation
+      // so we don't need to null-check the result of GetAnimation().
+      return aEffect.IsCurrent() && aEffect.GetAnimation()->AsCSSTransition();
+    }
+  );
+}
+
+bool
+nsLayoutUtils::HasAnimationOfProperty(const nsIFrame* aFrame,
+                                      nsCSSPropertyID aProperty)
+{
+  return HasMatchingAnimations(aFrame,
+    [&aProperty](KeyframeEffectReadOnly& aEffect)
+    {
+      return (aEffect.IsInEffect() || aEffect.IsCurrent()) &&
+             aEffect.HasAnimationOfProperty(aProperty);
+    }
+  );
+}
+
+bool
+nsLayoutUtils::HasEffectiveAnimation(const nsIFrame* aFrame,
+                                     nsCSSPropertyID aProperty)
+{
+  return HasMatchingAnimations(aFrame,
+    [&aProperty](KeyframeEffectReadOnly& aEffect)
+    {
+      return (aEffect.IsInEffect() || aEffect.IsCurrent()) &&
+             aEffect.HasEffectiveAnimationOfProperty(aProperty);
+    }
+  );
+}
+
+static float
+GetSuitableScale(float aMaxScale, float aMinScale,
+                 nscoord aVisibleDimension, nscoord aDisplayDimension)
+{
+  float displayVisibleRatio = float(aDisplayDimension) /
+                              float(aVisibleDimension);
+  // We want to rasterize based on the largest scale used during the
+  // transform animation, unless that would make us rasterize something
+  // larger than the screen.  But we never want to go smaller than the
+  // minimum scale over the animation.
+  if (FuzzyEqualsMultiplicative(displayVisibleRatio, aMaxScale, .01f)) {
+    // Using aMaxScale may make us rasterize something a fraction larger than
+    // the screen. However, if aMaxScale happens to be the final scale of a
+    // transform animation it is better to use aMaxScale so that for the
+    // fraction of a second before we delayerize the composited texture it has
+    // a better chance of being pixel aligned and composited without resampling
+    // (avoiding visually clunky delayerization).
+    return aMaxScale;
+  }
+  return std::max(std::min(aMaxScale, displayVisibleRatio), aMinScale);
+}
+
+static void
+GetMinAndMaxScaleForAnimationProperty(const nsIFrame* aFrame,
+                                      nsTArray<RefPtr<dom::Animation>>&
+                                        aAnimations,
+                                      gfxSize& aMaxScale,
+                                      gfxSize& aMinScale)
+{
+  for (dom::Animation* anim : aAnimations) {
+    // This method is only expected to be passed animations that are running on
+    // the compositor and we only pass playing animations to the compositor,
+    // which are, by definition, "relevant" animations (animations that are
+    // not yet finished or which are filling forwards).
+    MOZ_ASSERT(anim->IsRelevant());
+
+    dom::KeyframeEffectReadOnly* effect =
+      anim->GetEffect() ? anim->GetEffect()->AsKeyframeEffect() : nullptr;
+    MOZ_ASSERT(effect, "A playing animation should have a keyframe effect");
+    for (size_t propIdx = effect->Properties().Length(); propIdx-- != 0; ) {
+      const AnimationProperty& prop = effect->Properties()[propIdx];
+      if (prop.mProperty == eCSSProperty_transform) {
+        for (uint32_t segIdx = prop.mSegments.Length(); segIdx-- != 0; ) {
+          const AnimationPropertySegment& segment = prop.mSegments[segIdx];
+          gfxSize from = segment.mFromValue.GetScaleValue(aFrame);
+          aMaxScale.width = std::max<float>(aMaxScale.width, from.width);
+          aMaxScale.height = std::max<float>(aMaxScale.height, from.height);
+          aMinScale.width = std::min<float>(aMinScale.width, from.width);
+          aMinScale.height = std::min<float>(aMinScale.height, from.height);
+          gfxSize to = segment.mToValue.GetScaleValue(aFrame);
+          aMaxScale.width = std::max<float>(aMaxScale.width, to.width);
+          aMaxScale.height = std::max<float>(aMaxScale.height, to.height);
+          aMinScale.width = std::min<float>(aMinScale.width, to.width);
+          aMinScale.height = std::min<float>(aMinScale.height, to.height);
+        }
+      }
+    }
+  }
+}
+
+gfxSize
+nsLayoutUtils::ComputeSuitableScaleForAnimation(const nsIFrame* aFrame,
+                                                const nsSize& aVisibleSize,
+                                                const nsSize& aDisplaySize)
+{
+  gfxSize maxScale(std::numeric_limits<gfxFloat>::min(),
+                   std::numeric_limits<gfxFloat>::min());
+  gfxSize minScale(std::numeric_limits<gfxFloat>::max(),
+                   std::numeric_limits<gfxFloat>::max());
+
+  nsTArray<RefPtr<dom::Animation>> compositorAnimations =
+    EffectCompositor::GetAnimationsForCompositor(aFrame,
+                                                 eCSSProperty_transform);
+  GetMinAndMaxScaleForAnimationProperty(aFrame, compositorAnimations,
+                                        maxScale, minScale);
+
+  if (maxScale.width == std::numeric_limits<gfxFloat>::min()) {
+    // We didn't encounter a transform
+    return gfxSize(1.0, 1.0);
+  }
+
+  return gfxSize(GetSuitableScale(maxScale.width, minScale.width,
+                                  aVisibleSize.width, aDisplaySize.width),
+                 GetSuitableScale(maxScale.height, minScale.height,
+                                  aVisibleSize.height, aDisplaySize.height));
+}
+
+bool
+nsLayoutUtils::AreAsyncAnimationsEnabled()
+{
+  static bool sAreAsyncAnimationsEnabled;
+  static bool sAsyncPrefCached = false;
+
+  if (!sAsyncPrefCached) {
+    sAsyncPrefCached = true;
+    Preferences::AddBoolVarCache(&sAreAsyncAnimationsEnabled,
+                                 "layers.offmainthreadcomposition.async-animations");
+  }
+
+  return sAreAsyncAnimationsEnabled &&
+    gfxPlatform::OffMainThreadCompositingEnabled();
+}
+
+bool
+nsLayoutUtils::IsAnimationLoggingEnabled()
+{
+  static bool sShouldLog;
+  static bool sShouldLogPrefCached;
+
+  if (!sShouldLogPrefCached) {
+    sShouldLogPrefCached = true;
+    Preferences::AddBoolVarCache(&sShouldLog,
+                                 "layers.offmainthreadcomposition.log-animations");
+  }
+
+  return sShouldLog;
+}
+
+bool
+nsLayoutUtils::GPUImageScalingEnabled()
+{
+  static bool sGPUImageScalingEnabled;
+  static bool sGPUImageScalingPrefInitialised = false;
+
+  if (!sGPUImageScalingPrefInitialised) {
+    sGPUImageScalingPrefInitialised = true;
+    sGPUImageScalingEnabled =
+      Preferences::GetBool("layout.gpu-image-scaling.enabled", false);
+  }
+
+  return sGPUImageScalingEnabled;
+}
+
+bool
+nsLayoutUtils::AnimatedImageLayersEnabled()
+{
+  static bool sAnimatedImageLayersEnabled;
+  static bool sAnimatedImageLayersPrefCached = false;
+
+  if (!sAnimatedImageLayersPrefCached) {
+    sAnimatedImageLayersPrefCached = true;
+    Preferences::AddBoolVarCache(&sAnimatedImageLayersEnabled,
+                                 "layout.animated-image-layers.enabled",
+                                 false);
+  }
+
+  return sAnimatedImageLayersEnabled;
+}
+
+bool
+nsLayoutUtils::CSSFiltersEnabled()
+{
+  static bool sCSSFiltersEnabled;
+  static bool sCSSFiltersPrefCached = false;
+
+  if (!sCSSFiltersPrefCached) {
+    sCSSFiltersPrefCached = true;
+    Preferences::AddBoolVarCache(&sCSSFiltersEnabled,
+                                 "layout.css.filters.enabled",
+                                 false);
+  }
+
+  return sCSSFiltersEnabled;
+}
+
+bool
+nsLayoutUtils::CSSClipPathShapesEnabled()
+{
+  static bool sCSSClipPathShapesEnabled;
+  static bool sCSSClipPathShapesPrefCached = false;
+
+  if (!sCSSClipPathShapesPrefCached) {
+   sCSSClipPathShapesPrefCached = true;
+   Preferences::AddBoolVarCache(&sCSSClipPathShapesEnabled,
+                                "layout.css.clip-path-shapes.enabled",
+                                false);
+  }
+
+  return sCSSClipPathShapesEnabled;
+}
+
+bool
+nsLayoutUtils::UnsetValueEnabled()
+{
+  static bool sUnsetValueEnabled;
+  static bool sUnsetValuePrefCached = false;
+
+  if (!sUnsetValuePrefCached) {
+    sUnsetValuePrefCached = true;
+    Preferences::AddBoolVarCache(&sUnsetValueEnabled,
+                                 "layout.css.unset-value.enabled",
+                                 false);
+  }
+
+  return sUnsetValueEnabled;
+}
+
+bool
+nsLayoutUtils::IsGridTemplateSubgridValueEnabled()
+{
+  static bool sGridTemplateSubgridValueEnabled;
+  static bool sGridTemplateSubgridValueEnabledPrefCached = false;
+
+  if (!sGridTemplateSubgridValueEnabledPrefCached) {
+    sGridTemplateSubgridValueEnabledPrefCached = true;
+    Preferences::AddBoolVarCache(&sGridTemplateSubgridValueEnabled,
+                                 GRID_TEMPLATE_SUBGRID_ENABLED_PREF_NAME,
+                                 false);
+  }
+
+  return sGridTemplateSubgridValueEnabled;
+}
+
+bool
+nsLayoutUtils::IsTextAlignUnsafeValueEnabled()
+{
+  static bool sTextAlignUnsafeValueEnabled;
+  static bool sTextAlignUnsafeValueEnabledPrefCached = false;
+
+  if (!sTextAlignUnsafeValueEnabledPrefCached) {
+    sTextAlignUnsafeValueEnabledPrefCached = true;
+    Preferences::AddBoolVarCache(&sTextAlignUnsafeValueEnabled,
+                                 TEXT_ALIGN_UNSAFE_ENABLED_PREF_NAME,
+                                 false);
+  }
+
+  return sTextAlignUnsafeValueEnabled;
+}
+
+void
+nsLayoutUtils::UnionChildOverflow(nsIFrame* aFrame,
+                                  nsOverflowAreas& aOverflowAreas,
+                                  FrameChildListIDs aSkipChildLists)
+{
+  // Iterate over all children except pop-ups.
+  FrameChildListIDs skip = aSkipChildLists |
+      nsIFrame::kSelectPopupList | nsIFrame::kPopupList;
+  for (nsIFrame::ChildListIterator childLists(aFrame);
+       !childLists.IsDone(); childLists.Next()) {
+    if (skip.Contains(childLists.CurrentID())) {
+      continue;
+    }
+
+    nsFrameList children = childLists.CurrentList();
+    for (nsFrameList::Enumerator e(children); !e.AtEnd(); e.Next()) {
+      nsIFrame* child = e.get();
+      nsOverflowAreas childOverflow =
+        child->GetOverflowAreas() + child->GetPosition();
+      aOverflowAreas.UnionWith(childOverflow);
+    }
+  }
+}
+
+static void DestroyViewID(void* aObject, nsIAtom* aPropertyName,
+                          void* aPropertyValue, void* aData)
+{
+  ViewID* id = static_cast<ViewID*>(aPropertyValue);
+  GetContentMap().Remove(*id);
+  delete id;
+}
+
+/**
+ * A namespace class for static layout utilities.
+ */
+
+bool
+nsLayoutUtils::FindIDFor(const nsIContent* aContent, ViewID* aOutViewId)
+{
+  void* scrollIdProperty = aContent->GetProperty(nsGkAtoms::RemoteId);
+  if (scrollIdProperty) {
+    *aOutViewId = *static_cast<ViewID*>(scrollIdProperty);
+    return true;
+  }
+  return false;
+}
+
+ViewID
+nsLayoutUtils::FindOrCreateIDFor(nsIContent* aContent)
+{
+  ViewID scrollId;
+
+  if (!FindIDFor(aContent, &scrollId)) {
+    scrollId = sScrollIdCounter++;
+    aContent->SetProperty(nsGkAtoms::RemoteId, new ViewID(scrollId),
+                          DestroyViewID);
+    GetContentMap().Put(scrollId, aContent);
+  }
+
+  return scrollId;
+}
+
+nsIContent*
+nsLayoutUtils::FindContentFor(ViewID aId)
+{
+  MOZ_ASSERT(aId != FrameMetrics::NULL_SCROLL_ID,
+             "Cannot find a content element in map for null IDs.");
+  nsIContent* content;
+  bool exists = GetContentMap().Get(aId, &content);
+
+  if (exists) {
+    return content;
+  } else {
+    return nullptr;
+  }
+}
+
+nsIFrame*
+GetScrollFrameFromContent(nsIContent* aContent)
+{
+  nsIFrame* frame = aContent->GetPrimaryFrame();
+  if (aContent->OwnerDoc()->GetRootElement() == aContent) {
+    nsIPresShell* presShell = frame ? frame->PresContext()->PresShell() : nullptr;
+    if (!presShell) {
+      presShell = aContent->OwnerDoc()->GetShell();
+    }
+    // We want the scroll frame, the root scroll frame differs from all
+    // others in that the primary frame is not the scroll frame.
+    nsIFrame* rootScrollFrame = presShell ? presShell->GetRootScrollFrame() : nullptr;
+    if (rootScrollFrame) {
+      frame = rootScrollFrame;
+    }
+  }
+  return frame;
+}
+
+nsIScrollableFrame*
+nsLayoutUtils::FindScrollableFrameFor(ViewID aId)
+{
+  nsIContent* content = FindContentFor(aId);
+  if (!content) {
+    return nullptr;
+  }
+
+  nsIFrame* scrollFrame = GetScrollFrameFromContent(content);
+  return scrollFrame ? scrollFrame->GetScrollTargetFrame() : nullptr;
+}
+
+static nsRect
+ApplyRectMultiplier(nsRect aRect, float aMultiplier)
+{
+  if (aMultiplier == 1.0f) {
+    return aRect;
+  }
+  float newWidth = aRect.width * aMultiplier;
+  float newHeight = aRect.height * aMultiplier;
+  float newX = aRect.x - ((newWidth - aRect.width) / 2.0f);
+  float newY = aRect.y - ((newHeight - aRect.height) / 2.0f);
+  // Rounding doesn't matter too much here, do a round-in
+  return nsRect(ceil(newX), ceil(newY), floor(newWidth), floor(newHeight));
+}
+
+bool
+nsLayoutUtils::UsesAsyncScrolling(nsIFrame* aFrame)
+{
+#ifdef MOZ_WIDGET_ANDROID
+  // We always have async scrolling for android
+  return true;
+#endif
+
+  return AsyncPanZoomEnabled(aFrame);
+}
+
+bool
+nsLayoutUtils::AsyncPanZoomEnabled(nsIFrame* aFrame)
+{
+  // We use this as a shortcut, since if the compositor will never use APZ,
+  // no widget will either.
+  if (!gfxPlatform::AsyncPanZoomEnabled()) {
+    return false;
+  }
+
+  nsIFrame *frame = nsLayoutUtils::GetDisplayRootFrame(aFrame);
+  nsIWidget* widget = frame->GetNearestWidget();
+  if (!widget) {
+    return false;
+  }
+  return widget->AsyncPanZoomEnabled();
+}
+
+float
+nsLayoutUtils::GetCurrentAPZResolutionScale(nsIPresShell* aShell) {
+  return aShell ? aShell->GetCumulativeNonRootScaleResolution() : 1.0;
+}
+
+// Return the maximum displayport size, based on the LayerManager's maximum
+// supported texture size. The result is in app units.
+static nscoord
+GetMaxDisplayPortSize(nsIContent* aContent)
+{
+  MOZ_ASSERT(!gfxPrefs::LayersTilesEnabled(), "Do not clamp displayports if tiling is enabled");
+
+  nsIFrame* frame = aContent->GetPrimaryFrame();
+  if (!frame) {
+    return nscoord_MAX;
+  }
+  frame = nsLayoutUtils::GetDisplayRootFrame(frame);
+
+  nsIWidget* widget = frame->GetNearestWidget();
+  if (!widget) {
+    return nscoord_MAX;
+  }
+  LayerManager* lm = widget->GetLayerManager();
+  if (!lm) {
+    return nscoord_MAX;
+  }
+  nsPresContext* presContext = frame->PresContext();
+
+  int32_t maxSizeInDevPixels = lm->GetMaxTextureSize();
+  if (maxSizeInDevPixels < 0 || maxSizeInDevPixels == INT_MAX) {
+    return nscoord_MAX;
+  }
+  return presContext->DevPixelsToAppUnits(maxSizeInDevPixels);
+}
+
+static nsRect
+GetDisplayPortFromRectData(nsIContent* aContent,
+                           DisplayPortPropertyData* aRectData,
+                           float aMultiplier)
+{
+  // In the case where the displayport is set as a rect, we assume it is
+  // already aligned and clamped as necessary. The burden to do that is
+  // on the setter of the displayport. In practice very few places set the
+  // displayport directly as a rect (mostly tests). We still do need to
+  // expand it by the multiplier though.
+  return ApplyRectMultiplier(aRectData->mRect, aMultiplier);
+}
+
+static nsRect
+GetDisplayPortFromMarginsData(nsIContent* aContent,
+                              DisplayPortMarginsPropertyData* aMarginsData,
+                              float aMultiplier)
+{
+  // In the case where the displayport is set via margins, we apply the margins
+  // to a base rect. Then we align the expanded rect based on the alignment
+  // requested, further expand the rect by the multiplier, and finally, clamp it
+  // to the size of the scrollable rect.
+
+  nsRect base;
+  if (nsRect* baseData = static_cast<nsRect*>(aContent->GetProperty(nsGkAtoms::DisplayPortBase))) {
+    base = *baseData;
+  } else {
+    // In theory we shouldn't get here, but we do sometimes (see bug 1212136).
+    // Fall through for graceful handling.
+  }
+
+  nsIFrame* frame = GetScrollFrameFromContent(aContent);
+  if (!frame) {
+    // Turns out we can't really compute it. Oops. We still should return
+    // something sane. Note that since we can't clamp the rect without a
+    // frame, we don't apply the multiplier either as it can cause the result
+    // to leak outside the scrollable area.
+    NS_WARNING("Attempting to get a displayport from a content with no primary frame!");
+    return base;
+  }
+
+  bool isRoot = false;
+  if (aContent->OwnerDoc()->GetRootElement() == aContent) {
+    isRoot = true;
+  }
+
+  nsPoint scrollPos;
+  if (nsIScrollableFrame* scrollableFrame = frame->GetScrollTargetFrame()) {
+    scrollPos = scrollableFrame->GetScrollPosition();
+  }
+
+  nsPresContext* presContext = frame->PresContext();
+  int32_t auPerDevPixel = presContext->AppUnitsPerDevPixel();
+
+  LayoutDeviceToScreenScale2D res(presContext->PresShell()->GetCumulativeResolution()
+                                * nsLayoutUtils::GetTransformToAncestorScale(frame));
+
+  // Calculate the expanded scrollable rect, which we'll be clamping the
+  // displayport to.
+  nsRect expandedScrollableRect =
+    nsLayoutUtils::CalculateExpandedScrollableRect(frame);
+
+  // GetTransformToAncestorScale() can return 0. In this case, just return the
+  // base rect (clamped to the expanded scrollable rect), as other calculations
+  // would run into divisions by zero.
+  if (res == LayoutDeviceToScreenScale2D(0, 0)) {
+    // Make sure the displayport remains within the scrollable rect.
+    return base.MoveInsideAndClamp(expandedScrollableRect - scrollPos);
+  }
+
+  // First convert the base rect to screen pixels
+  LayoutDeviceToScreenScale2D parentRes = res;
+  if (isRoot) {
+    // the base rect for root scroll frames is specified in the parent document
+    // coordinate space, so it doesn't include the local resolution.
+    float localRes = presContext->PresShell()->GetResolution();
+    parentRes.xScale /= localRes;
+    parentRes.yScale /= localRes;
+  }
+  ScreenRect screenRect = LayoutDeviceRect::FromAppUnits(base, auPerDevPixel)
+                        * parentRes;
+
+  // Note on the correctness of applying the alignment in Screen space:
+  //   The correct space to apply the alignment in would be Layer space, but
+  //   we don't necessarily know the scale to convert to Layer space at this
+  //   point because Layout may not yet have chosen the resolution at which to
+  //   render (it chooses that in FrameLayerBuilder, but this can be called
+  //   during display list building). Therefore, we perform the alignment in
+  //   Screen space, which basically assumes that Layout chose to render at
+  //   screen resolution; since this is what Layout does most of the time,
+  //   this is a good approximation. A proper solution would involve moving
+  //   the choosing of the resolution to display-list building time.
+  ScreenSize alignment;
+
+  if (APZCCallbackHelper::IsDisplayportSuppressed()) {
+    alignment = ScreenSize(1, 1);
+  } else if (gfxPrefs::LayersTilesEnabled()) {
+    // Don't align to tiles if they are too large, because we could expand
+    // the displayport by a lot which can take more paint time. It's a tradeoff
+    // though because if we don't align to tiles we have more waste on upload.
+    IntSize tileSize = gfxVars::TileSize();
+    alignment = ScreenSize(std::min(256, tileSize.width), std::min(256, tileSize.height));
+  } else {
+    // If we're not drawing with tiles then we need to be careful about not
+    // hitting the max texture size and we only need 1 draw call per layer
+    // so we can align to a smaller multiple.
+    alignment = ScreenSize(128, 128);
+  }
+
+  // Avoid division by zero.
+  if (alignment.width == 0) {
+    alignment.width = 128;
+  }
+  if (alignment.height == 0) {
+    alignment.height = 128;
+  }
+
+  if (gfxPrefs::LayersTilesEnabled()) {
+    // Expand the rect by the margins
+    screenRect.Inflate(aMarginsData->mMargins);
+  } else {
+    // Calculate the displayport to make sure we fit within the max texture size
+    // when not tiling.
+    nscoord maxSizeAppUnits = GetMaxDisplayPortSize(aContent);
+    if (maxSizeAppUnits == nscoord_MAX) {
+      // Pick a safe maximum displayport size for sanity purposes. This is the
+      // lowest maximum texture size on tileless-platforms (Windows, D3D10).
+      maxSizeAppUnits = presContext->DevPixelsToAppUnits(8192);
+    }
+
+    // The alignment code can round up to 3 tiles, we want to make sure
+    // that the displayport can grow by up to 3 tiles without going
+    // over the max texture size.
+    const int MAX_ALIGN_ROUNDING = 3;
+
+    // Find the maximum size in screen pixels.
+    int32_t maxSizeDevPx = presContext->AppUnitsToDevPixels(maxSizeAppUnits);
+    int32_t maxWidthScreenPx = floor(double(maxSizeDevPx) * res.xScale) -
+      MAX_ALIGN_ROUNDING * alignment.width;
+    int32_t maxHeightScreenPx = floor(double(maxSizeDevPx) * res.yScale) -
+      MAX_ALIGN_ROUNDING * alignment.height;
+
+    // For each axis, inflate the margins up to the maximum size.
+    const ScreenMargin& margins = aMarginsData->mMargins;
+    if (screenRect.height < maxHeightScreenPx) {
+      int32_t budget = maxHeightScreenPx - screenRect.height;
+      // Scale the margins down to fit into the budget if necessary, maintaining
+      // their relative ratio.
+      float scale = std::min(1.0f, float(budget) / margins.TopBottom());
+      float top = margins.top * scale;
+      float bottom = margins.bottom * scale;
+      screenRect.y -= top;
+      screenRect.height += top + bottom;
+    }
+    if (screenRect.width < maxWidthScreenPx) {
+      int32_t budget = maxWidthScreenPx - screenRect.width;
+      float scale = std::min(1.0f, float(budget) / margins.LeftRight());
+      float left = margins.left * scale;
+      float right = margins.right * scale;
+      screenRect.x -= left;
+      screenRect.width += left + right;
+    }
+  }
+
+  ScreenPoint scrollPosScreen = LayoutDevicePoint::FromAppUnits(scrollPos, auPerDevPixel)
+                              * res;
+
+  // Round-out the display port to the nearest alignment (tiles)
+  screenRect += scrollPosScreen;
+  float x = alignment.width * floor(screenRect.x / alignment.width);
+  float y = alignment.height * floor(screenRect.y / alignment.height);
+  float w = alignment.width * ceil(screenRect.width / alignment.width + 1);
+  float h = alignment.height * ceil(screenRect.height / alignment.height + 1);
+  screenRect = ScreenRect(x, y, w, h);
+  screenRect -= scrollPosScreen;
+
+  // Convert the aligned rect back into app units.
+  nsRect result = LayoutDeviceRect::ToAppUnits(screenRect / res, auPerDevPixel);
+
+  // If we have non-zero margins, expand the displayport for the low-res buffer
+  // if that's what we're drawing. If we have zero margins, we want the
+  // displayport to reflect the scrollport.
+  if (aMarginsData->mMargins != ScreenMargin()) {
+    result = ApplyRectMultiplier(result, aMultiplier);
+  }
+
+  // Make sure the displayport remains within the scrollable rect.
+  result = result.MoveInsideAndClamp(expandedScrollableRect - scrollPos);
+
+  return result;
+}
+
+static bool
+ShouldDisableApzForElement(nsIContent* aContent)
+{
+  if (gfxPrefs::APZDisableForScrollLinkedEffects() && aContent) {
+    nsIDocument* doc = aContent->GetComposedDoc();
+    return (doc && doc->HasScrollLinkedEffect());
+  }
+  return false;
+}
+
+static bool
+GetDisplayPortImpl(nsIContent* aContent, nsRect *aResult, float aMultiplier)
+{
+  DisplayPortPropertyData* rectData =
+    static_cast<DisplayPortPropertyData*>(aContent->GetProperty(nsGkAtoms::DisplayPort));
+  DisplayPortMarginsPropertyData* marginsData =
+    static_cast<DisplayPortMarginsPropertyData*>(aContent->GetProperty(nsGkAtoms::DisplayPortMargins));
+
+  if (!rectData && !marginsData) {
+    // This content element has no displayport data at all
+    return false;
+  }
+
+  if (!aResult) {
+    // We have displayport data, but the caller doesn't want the actual
+    // rect, so we don't need to actually compute it.
+    return true;
+  }
+
+  if (rectData && marginsData) {
+    // choose margins if equal priority
+    if (rectData->mPriority > marginsData->mPriority) {
+      marginsData = nullptr;
+    } else {
+      rectData = nullptr;
+    }
+  }
+
+  NS_ASSERTION((rectData == nullptr) != (marginsData == nullptr),
+               "Only one of rectData or marginsData should be set!");
+
+  nsRect result;
+  if (rectData) {
+    result = GetDisplayPortFromRectData(aContent, rectData, aMultiplier);
+  } else if (APZCCallbackHelper::IsDisplayportSuppressed() || ShouldDisableApzForElement(aContent)) {
+    DisplayPortMarginsPropertyData noMargins(ScreenMargin(), 1);
+    result = GetDisplayPortFromMarginsData(aContent, &noMargins, aMultiplier);
+  } else {
+    result = GetDisplayPortFromMarginsData(aContent, marginsData, aMultiplier);
+  }
+
+  if (!gfxPrefs::LayersTilesEnabled()) {
+    // Either we should have gotten a valid rect directly from the displayport
+    // base, or we should have computed a valid rect from the margins.
+    NS_ASSERTION(result.width <= GetMaxDisplayPortSize(aContent),
+                 "Displayport must be a valid texture size");
+    NS_ASSERTION(result.height <= GetMaxDisplayPortSize(aContent),
+                 "Displayport must be a valid texture size");
+  }
+
+  *aResult = result;
+  return true;
+}
+
+void
+TranslateFromScrollPortToScrollFrame(nsIContent* aContent, nsRect* aRect)
+{
+  MOZ_ASSERT(aRect);
+  nsIFrame* frame = GetScrollFrameFromContent(aContent);
+  nsIScrollableFrame* scrollableFrame = frame ? frame->GetScrollTargetFrame() : nullptr;
+  if (scrollableFrame) {
+    *aRect += scrollableFrame->GetScrollPortRect().TopLeft();
+  }
+}
+
+bool
+nsLayoutUtils::GetDisplayPort(nsIContent* aContent, nsRect *aResult,
+  RelativeTo aRelativeTo /* = RelativeTo::ScrollPort */)
+{
+  float multiplier =
+    gfxPrefs::UseLowPrecisionBuffer() ? 1.0f / gfxPrefs::LowPrecisionResolution() : 1.0f;
+  bool usingDisplayPort = GetDisplayPortImpl(aContent, aResult, multiplier);
+  if (aResult && usingDisplayPort && aRelativeTo == RelativeTo::ScrollFrame) {
+    TranslateFromScrollPortToScrollFrame(aContent, aResult);
+  }
+  return usingDisplayPort;
+}
+
+bool
+nsLayoutUtils::HasDisplayPort(nsIContent* aContent) {
+  return GetDisplayPort(aContent, nullptr);
+}
+
+/* static */ bool
+nsLayoutUtils::GetDisplayPortForVisibilityTesting(
+  nsIContent* aContent,
+  nsRect* aResult,
+  RelativeTo aRelativeTo /* = RelativeTo::ScrollPort */)
+{
+  MOZ_ASSERT(aResult);
+  bool usingDisplayPort = GetDisplayPortImpl(aContent, aResult, 1.0f);
+  if (usingDisplayPort && aRelativeTo == RelativeTo::ScrollFrame) {
+    TranslateFromScrollPortToScrollFrame(aContent, aResult);
+  }
+  return usingDisplayPort;
+}
+
+bool
+nsLayoutUtils::SetDisplayPortMargins(nsIContent* aContent,
+                                     nsIPresShell* aPresShell,
+                                     const ScreenMargin& aMargins,
+                                     uint32_t aPriority,
+                                     RepaintMode aRepaintMode)
+{
+  MOZ_ASSERT(aContent);
+  MOZ_ASSERT(aContent->GetComposedDoc() == aPresShell->GetDocument());
+
+  DisplayPortMarginsPropertyData* currentData =
+    static_cast<DisplayPortMarginsPropertyData*>(aContent->GetProperty(nsGkAtoms::DisplayPortMargins));
+  if (currentData && currentData->mPriority > aPriority) {
+    return false;
+  }
+
+  nsRect oldDisplayPort;
+  bool hadDisplayPort = GetHighResolutionDisplayPort(aContent, &oldDisplayPort);
+
+  aContent->SetProperty(nsGkAtoms::DisplayPortMargins,
+                        new DisplayPortMarginsPropertyData(
+                            aMargins, aPriority),
+                        nsINode::DeleteProperty<DisplayPortMarginsPropertyData>);
+
+  nsRect newDisplayPort;
+  DebugOnly<bool> hasDisplayPort = GetHighResolutionDisplayPort(aContent, &newDisplayPort);
+  MOZ_ASSERT(hasDisplayPort);
+
+  bool changed = !hadDisplayPort ||
+        !oldDisplayPort.IsEqualEdges(newDisplayPort);
+
+  if (gfxPrefs::LayoutUseContainersForRootFrames()) {
+    nsIFrame* rootScrollFrame = aPresShell->GetRootScrollFrame();
+    if (rootScrollFrame &&
+        aContent == rootScrollFrame->GetContent() &&
+        nsLayoutUtils::UsesAsyncScrolling(rootScrollFrame))
+    {
+      // We are setting a root displayport for a document.
+      // If we have APZ, then set a special flag on the pres shell so
+      // that we don't get scrollbars drawn.
+      aPresShell->SetIgnoreViewportScrolling(true);
+    }
+  }
+
+  if (changed && aRepaintMode == RepaintMode::Repaint) {
+    nsIFrame* frame = aContent->GetPrimaryFrame();
+    if (frame) {
+      frame->SchedulePaint();
+    }
+  }
+
+  nsIFrame* frame = GetScrollFrameFromContent(aContent);
+  nsIScrollableFrame* scrollableFrame = frame ? frame->GetScrollTargetFrame() : nullptr;
+  if (!scrollableFrame) {
+    return true;
+  }
+
+  scrollableFrame->TriggerDisplayPortExpiration();
+
+  // Display port margins changing means that the set of visible frames may
+  // have drastically changed. Check if we should schedule an update.
+  hadDisplayPort =
+    scrollableFrame->GetDisplayPortAtLastApproximateFrameVisibilityUpdate(&oldDisplayPort);
+
+  bool needVisibilityUpdate = !hadDisplayPort;
+  // Check if the total size has changed by a large factor.
+  if (!needVisibilityUpdate) {
+    if ((newDisplayPort.width > 2 * oldDisplayPort.width) ||
+        (oldDisplayPort.width > 2 * newDisplayPort.width) ||
+        (newDisplayPort.height > 2 * oldDisplayPort.height) ||
+        (oldDisplayPort.height > 2 * newDisplayPort.height)) {
+      needVisibilityUpdate = true;
+    }
+  }
+  // Check if it's moved by a significant amount.
+  if (!needVisibilityUpdate) {
+    if (nsRect* baseData = static_cast<nsRect*>(aContent->GetProperty(nsGkAtoms::DisplayPortBase))) {
+      nsRect base = *baseData;
+      if ((std::abs(newDisplayPort.X() - oldDisplayPort.X()) > base.width) ||
+          (std::abs(newDisplayPort.XMost() - oldDisplayPort.XMost()) > base.width) ||
+          (std::abs(newDisplayPort.Y() - oldDisplayPort.Y()) > base.height) ||
+          (std::abs(newDisplayPort.YMost() - oldDisplayPort.YMost()) > base.height)) {
+        needVisibilityUpdate = true;
+      }
+    }
+  }
+  if (needVisibilityUpdate) {
+    aPresShell->ScheduleApproximateFrameVisibilityUpdateNow();
+  }
+
+  return true;
+}
+
+void
+nsLayoutUtils::SetDisplayPortBase(nsIContent* aContent, const nsRect& aBase)
+{
+  aContent->SetProperty(nsGkAtoms::DisplayPortBase, new nsRect(aBase),
+                        nsINode::DeleteProperty<nsRect>);
+}
+
+void
+nsLayoutUtils::SetDisplayPortBaseIfNotSet(nsIContent* aContent, const nsRect& aBase)
+{
+  if (!aContent->GetProperty(nsGkAtoms::DisplayPortBase)) {
+    SetDisplayPortBase(aContent, aBase);
+  }
+}
+
+bool
+nsLayoutUtils::GetCriticalDisplayPort(nsIContent* aContent, nsRect* aResult)
+{
+  if (gfxPrefs::UseLowPrecisionBuffer()) {
+    return GetDisplayPortImpl(aContent, aResult, 1.0f);
+  }
+  return false;
+}
+
+bool
+nsLayoutUtils::HasCriticalDisplayPort(nsIContent* aContent)
+{
+  return GetCriticalDisplayPort(aContent, nullptr);
+}
+
+bool
+nsLayoutUtils::GetHighResolutionDisplayPort(nsIContent* aContent, nsRect* aResult)
+{
+  if (gfxPrefs::UseLowPrecisionBuffer()) {
+    return GetCriticalDisplayPort(aContent, aResult);
+  }
+  return GetDisplayPort(aContent, aResult);
+}
+
+void
+nsLayoutUtils::RemoveDisplayPort(nsIContent* aContent)
+{
+  aContent->DeleteProperty(nsGkAtoms::DisplayPort);
+  aContent->DeleteProperty(nsGkAtoms::DisplayPortMargins);
+}
+
+nsContainerFrame*
+nsLayoutUtils::LastContinuationWithChild(nsContainerFrame* aFrame)
+{
+  NS_PRECONDITION(aFrame, "NULL frame pointer");
+  nsIFrame* f = aFrame->LastContinuation();
+  while (!f->PrincipalChildList().FirstChild() && f->GetPrevContinuation()) {
+    f = f->GetPrevContinuation();
+  }
+  return static_cast<nsContainerFrame*>(f);
+}
+
+//static
+FrameChildListID
+nsLayoutUtils::GetChildListNameFor(nsIFrame* aChildFrame)
+{
+  nsIFrame::ChildListID id = nsIFrame::kPrincipalList;
+
+  if (aChildFrame->GetStateBits() & NS_FRAME_IS_OVERFLOW_CONTAINER) {
+    nsIFrame* pif = aChildFrame->GetPrevInFlow();
+    if (pif->GetParent() == aChildFrame->GetParent()) {
+      id = nsIFrame::kExcessOverflowContainersList;
+    }
+    else {
+      id = nsIFrame::kOverflowContainersList;
+    }
+  }
+  // See if the frame is moved out of the flow
+  else if (aChildFrame->GetStateBits() & NS_FRAME_OUT_OF_FLOW) {
+    // Look at the style information to tell
+    const nsStyleDisplay* disp = aChildFrame->StyleDisplay();
+
+    if (NS_STYLE_POSITION_ABSOLUTE == disp->mPosition) {
+      id = nsIFrame::kAbsoluteList;
+    } else if (NS_STYLE_POSITION_FIXED == disp->mPosition) {
+      if (nsLayoutUtils::IsReallyFixedPos(aChildFrame)) {
+        id = nsIFrame::kFixedList;
+      } else {
+        id = nsIFrame::kAbsoluteList;
+      }
+#ifdef MOZ_XUL
+    } else if (StyleDisplay::Popup == disp->mDisplay) {
+      // Out-of-flows that are DISPLAY_POPUP must be kids of the root popup set
+#ifdef DEBUG
+      nsIFrame* parent = aChildFrame->GetParent();
+      NS_ASSERTION(parent && parent->GetType() == nsGkAtoms::popupSetFrame,
+                   "Unexpected parent");
+#endif // DEBUG
+
+      id = nsIFrame::kPopupList;
+#endif // MOZ_XUL
+    } else {
+      NS_ASSERTION(aChildFrame->IsFloating(), "not a floated frame");
+      id = nsIFrame::kFloatList;
+    }
+
+  } else {
+    nsIAtom* childType = aChildFrame->GetType();
+    if (nsGkAtoms::menuPopupFrame == childType) {
+      nsIFrame* parent = aChildFrame->GetParent();
+      MOZ_ASSERT(parent, "nsMenuPopupFrame can't be the root frame");
+      if (parent) {
+        if (parent->GetType() == nsGkAtoms::popupSetFrame) {
+          id = nsIFrame::kPopupList;
+        } else {
+          nsIFrame* firstPopup = parent->GetChildList(nsIFrame::kPopupList).FirstChild();
+          MOZ_ASSERT(!firstPopup || !firstPopup->GetNextSibling(),
+                     "We assume popupList only has one child, but it has more.");
+          id = firstPopup == aChildFrame
+                 ? nsIFrame::kPopupList
+                 : nsIFrame::kPrincipalList;
+        }
+      } else {
+        id = nsIFrame::kPrincipalList;
+      }
+    } else if (nsGkAtoms::tableColGroupFrame == childType) {
+      id = nsIFrame::kColGroupList;
+    } else if (aChildFrame->IsTableCaption()) {
+      id = nsIFrame::kCaptionList;
+    } else {
+      id = nsIFrame::kPrincipalList;
+    }
+  }
+
+#ifdef DEBUG
+  // Verify that the frame is actually in that child list or in the
+  // corresponding overflow list.
+  nsContainerFrame* parent = aChildFrame->GetParent();
+  bool found = parent->GetChildList(id).ContainsFrame(aChildFrame);
+  if (!found) {
+    if (!(aChildFrame->GetStateBits() & NS_FRAME_OUT_OF_FLOW)) {
+      found = parent->GetChildList(nsIFrame::kOverflowList)
+                .ContainsFrame(aChildFrame);
+    }
+    else if (aChildFrame->IsFloating()) {
+      found = parent->GetChildList(nsIFrame::kOverflowOutOfFlowList)
+                .ContainsFrame(aChildFrame);
+      if (!found) {
+        found = parent->GetChildList(nsIFrame::kPushedFloatsList)
+                  .ContainsFrame(aChildFrame);
+      }
+    }
+    // else it's positioned and should have been on the 'id' child list.
+    NS_POSTCONDITION(found, "not in child list");
+  }
+#endif
+
+  return id;
+}
+
+/*static*/ nsIFrame*
+nsLayoutUtils::GetBeforeFrameForContent(nsIFrame* aFrame,
+                                        const nsIContent* aContent)
+{
+  // We need to call GetGenConPseudos() on the first continuation/ib-split.
+  // Find it, for symmetry with GetAfterFrameForContent.
+  nsContainerFrame* genConParentFrame =
+    FirstContinuationOrIBSplitSibling(aFrame)->GetContentInsertionFrame();
+  if (!genConParentFrame) {
+    return nullptr;
+  }
+  nsTArray<nsIContent*>* prop = genConParentFrame->GetGenConPseudos();
+  if (prop) {
+    const nsTArray<nsIContent*>& pseudos(*prop);
+    for (uint32_t i = 0; i < pseudos.Length(); ++i) {
+      if (pseudos[i]->GetParent() == aContent &&
+          pseudos[i]->NodeInfo()->NameAtom() == nsGkAtoms::mozgeneratedcontentbefore) {
+        return pseudos[i]->GetPrimaryFrame();
+      }
+    }
+  }
+  // If the first child frame is a pseudo-frame, then try that.
+  // Note that the frame we create for the generated content is also a
+  // pseudo-frame and so don't drill down in that case.
+  nsIFrame* childFrame = genConParentFrame->PrincipalChildList().FirstChild();
+  if (childFrame &&
+      childFrame->IsPseudoFrame(aContent) &&
+      !childFrame->IsGeneratedContentFrame()) {
+    return GetBeforeFrameForContent(childFrame, aContent);
+  }
+  return nullptr;
+}
+
+/*static*/ nsIFrame*
+nsLayoutUtils::GetBeforeFrame(nsIFrame* aFrame)
+{
+  return GetBeforeFrameForContent(aFrame, aFrame->GetContent());
+}
+
+/*static*/ nsIFrame*
+nsLayoutUtils::GetAfterFrameForContent(nsIFrame* aFrame,
+                                       const nsIContent* aContent)
+{
+  // We need to call GetGenConPseudos() on the first continuation,
+  // but callers are likely to pass the last.
+  nsContainerFrame* genConParentFrame =
+    FirstContinuationOrIBSplitSibling(aFrame)->GetContentInsertionFrame();
+  if (!genConParentFrame) {
+    return nullptr;
+  }
+  nsTArray<nsIContent*>* prop = genConParentFrame->GetGenConPseudos();
+  if (prop) {
+    const nsTArray<nsIContent*>& pseudos(*prop);
+    for (uint32_t i = 0; i < pseudos.Length(); ++i) {
+      if (pseudos[i]->GetParent() == aContent &&
+          pseudos[i]->NodeInfo()->NameAtom() == nsGkAtoms::mozgeneratedcontentafter) {
+        return pseudos[i]->GetPrimaryFrame();
+      }
+    }
+  }
+  // If the last child frame is a pseudo-frame, then try that.
+  // Note that the frame we create for the generated content is also a
+  // pseudo-frame and so don't drill down in that case.
+  genConParentFrame = aFrame->GetContentInsertionFrame();
+  if (!genConParentFrame) {
+    return nullptr;
+  }
+  nsIFrame* lastParentContinuation =
+    LastContinuationWithChild(static_cast<nsContainerFrame*>(
+      LastContinuationOrIBSplitSibling(genConParentFrame)));
+  nsIFrame* childFrame =
+    lastParentContinuation->GetChildList(nsIFrame::kPrincipalList).LastChild();
+  if (childFrame &&
+      childFrame->IsPseudoFrame(aContent) &&
+      !childFrame->IsGeneratedContentFrame()) {
+    return GetAfterFrameForContent(childFrame->FirstContinuation(), aContent);
+  }
+  return nullptr;
+}
+
+/*static*/ nsIFrame*
+nsLayoutUtils::GetAfterFrame(nsIFrame* aFrame)
+{
+  return GetAfterFrameForContent(aFrame, aFrame->GetContent());
+}
+
+// static
+nsIFrame*
+nsLayoutUtils::GetClosestFrameOfType(nsIFrame* aFrame,
+                                     nsIAtom* aFrameType,
+                                     nsIFrame* aStopAt)
+{
+  for (nsIFrame* frame = aFrame; frame; frame = frame->GetParent()) {
+    if (frame->GetType() == aFrameType) {
+      return frame;
+    }
+    if (frame == aStopAt) {
+      break;
+    }
+  }
+  return nullptr;
+}
+
+// static
+nsIFrame*
+nsLayoutUtils::GetStyleFrame(nsIFrame* aFrame)
+{
+  if (aFrame->GetType() == nsGkAtoms::tableWrapperFrame) {
+    nsIFrame* inner = aFrame->PrincipalChildList().FirstChild();
+    // inner may be null, if aFrame is mid-destruction
+    return inner;
+  }
+
+  return aFrame;
+}
+
+nsIFrame*
+nsLayoutUtils::GetStyleFrame(const nsIContent* aContent)
+{
+  nsIFrame *frame = aContent->GetPrimaryFrame();
+  if (!frame) {
+    return nullptr;
+  }
+
+  return nsLayoutUtils::GetStyleFrame(frame);
+}
+
+/* static */ nsIFrame*
+nsLayoutUtils::GetRealPrimaryFrameFor(const nsIContent* aContent)
+{
+  nsIFrame *frame = aContent->GetPrimaryFrame();
+  if (!frame) {
+    return nullptr;
+  }
+
+  return nsPlaceholderFrame::GetRealFrameFor(frame);
+}
+
+nsIFrame*
+nsLayoutUtils::GetFloatFromPlaceholder(nsIFrame* aFrame) {
+  NS_ASSERTION(nsGkAtoms::placeholderFrame == aFrame->GetType(),
+               "Must have a placeholder here");
+  if (aFrame->GetStateBits() & PLACEHOLDER_FOR_FLOAT) {
+    nsIFrame *outOfFlowFrame =
+      nsPlaceholderFrame::GetRealFrameForPlaceholder(aFrame);
+    NS_ASSERTION(outOfFlowFrame->IsFloating(),
+                 "How did that happen?");
+    return outOfFlowFrame;
+  }
+
+  return nullptr;
+}
+
+// static
+bool
+nsLayoutUtils::IsGeneratedContentFor(nsIContent* aContent,
+                                     nsIFrame* aFrame,
+                                     nsIAtom* aPseudoElement)
+{
+  NS_PRECONDITION(aFrame, "Must have a frame");
+  NS_PRECONDITION(aPseudoElement, "Must have a pseudo name");
+
+  if (!aFrame->IsGeneratedContentFrame()) {
+    return false;
+  }
+  nsIFrame* parent = aFrame->GetParent();
+  NS_ASSERTION(parent, "Generated content can't be root frame");
+  if (parent->IsGeneratedContentFrame()) {
+    // Not the root of the generated content
+    return false;
+  }
+
+  if (aContent && parent->GetContent() != aContent) {
+    return false;
+  }
+
+  return (aFrame->GetContent()->NodeInfo()->NameAtom() == nsGkAtoms::mozgeneratedcontentbefore) ==
+    (aPseudoElement == nsCSSPseudoElements::before);
+}
+
+// static
+nsIFrame*
+nsLayoutUtils::GetCrossDocParentFrame(const nsIFrame* aFrame,
+                                      nsPoint* aExtraOffset)
+{
+  nsIFrame* p = aFrame->GetParent();
+  if (p)
+    return p;
+
+  nsView* v = aFrame->GetView();
+  if (!v)
+    return nullptr;
+  v = v->GetParent(); // anonymous inner view
+  if (!v)
+    return nullptr;
+  if (aExtraOffset) {
+    *aExtraOffset += v->GetPosition();
+  }
+  v = v->GetParent(); // subdocumentframe's view
+  return v ? v->GetFrame() : nullptr;
+}
+
+// static
+bool
+nsLayoutUtils::IsProperAncestorFrameCrossDoc(nsIFrame* aAncestorFrame, nsIFrame* aFrame,
+                                             nsIFrame* aCommonAncestor)
+{
+  if (aFrame == aAncestorFrame)
+    return false;
+  return IsAncestorFrameCrossDoc(aAncestorFrame, aFrame, aCommonAncestor);
+}
+
+// static
+bool
+nsLayoutUtils::IsAncestorFrameCrossDoc(const nsIFrame* aAncestorFrame, const nsIFrame* aFrame,
+                                       const nsIFrame* aCommonAncestor)
+{
+  for (const nsIFrame* f = aFrame; f != aCommonAncestor;
+       f = GetCrossDocParentFrame(f)) {
+    if (f == aAncestorFrame)
+      return true;
+  }
+  return aCommonAncestor == aAncestorFrame;
+}
+
+// static
+bool
+nsLayoutUtils::IsProperAncestorFrame(nsIFrame* aAncestorFrame, nsIFrame* aFrame,
+                                     nsIFrame* aCommonAncestor)
+{
+  if (aFrame == aAncestorFrame)
+    return false;
+  for (nsIFrame* f = aFrame; f != aCommonAncestor; f = f->GetParent()) {
+    if (f == aAncestorFrame)
+      return true;
+  }
+  return aCommonAncestor == aAncestorFrame;
+}
+
+// static
+int32_t
+nsLayoutUtils::DoCompareTreePosition(nsIContent* aContent1,
+                                     nsIContent* aContent2,
+                                     int32_t aIf1Ancestor,
+                                     int32_t aIf2Ancestor,
+                                     const nsIContent* aCommonAncestor)
+{
+  NS_PRECONDITION(aContent1, "aContent1 must not be null");
+  NS_PRECONDITION(aContent2, "aContent2 must not be null");
+
+  AutoTArray<nsINode*, 32> content1Ancestors;
+  nsINode* c1;
+  for (c1 = aContent1; c1 && c1 != aCommonAncestor; c1 = c1->GetParentNode()) {
+    content1Ancestors.AppendElement(c1);
+  }
+  if (!c1 && aCommonAncestor) {
+    // So, it turns out aCommonAncestor was not an ancestor of c1. Oops.
+    // Never mind. We can continue as if aCommonAncestor was null.
+    aCommonAncestor = nullptr;
+  }
+
+  AutoTArray<nsINode*, 32> content2Ancestors;
+  nsINode* c2;
+  for (c2 = aContent2; c2 && c2 != aCommonAncestor; c2 = c2->GetParentNode()) {
+    content2Ancestors.AppendElement(c2);
+  }
+  if (!c2 && aCommonAncestor) {
+    // So, it turns out aCommonAncestor was not an ancestor of c2.
+    // We need to retry with no common ancestor hint.
+    return DoCompareTreePosition(aContent1, aContent2,
+                                 aIf1Ancestor, aIf2Ancestor, nullptr);
+  }
+
+  int last1 = content1Ancestors.Length() - 1;
+  int last2 = content2Ancestors.Length() - 1;
+  nsINode* content1Ancestor = nullptr;
+  nsINode* content2Ancestor = nullptr;
+  while (last1 >= 0 && last2 >= 0
+         && ((content1Ancestor = content1Ancestors.ElementAt(last1)) ==
+             (content2Ancestor = content2Ancestors.ElementAt(last2)))) {
+    last1--;
+    last2--;
+  }
+
+  if (last1 < 0) {
+    if (last2 < 0) {
+      NS_ASSERTION(aContent1 == aContent2, "internal error?");
+      return 0;
+    }
+    // aContent1 is an ancestor of aContent2
+    return aIf1Ancestor;
+  }
+
+  if (last2 < 0) {
+    // aContent2 is an ancestor of aContent1
+    return aIf2Ancestor;
+  }
+
+  // content1Ancestor != content2Ancestor, so they must be siblings with the same parent
+  nsINode* parent = content1Ancestor->GetParentNode();
+#ifdef DEBUG
+  // TODO: remove the uglyness, see bug 598468.
+  NS_ASSERTION(gPreventAssertInCompareTreePosition || parent,
+               "no common ancestor at all???");
+#endif // DEBUG
+  if (!parent) { // different documents??
+    return 0;
+  }
+
+  int32_t index1 = parent->IndexOf(content1Ancestor);
+  int32_t index2 = parent->IndexOf(content2Ancestor);
+  if (index1 < 0 || index2 < 0) {
+    // one of them must be anonymous; we can't determine the order
+    return 0;
+  }
+
+  return index1 - index2;
+}
+
+// static
+nsIFrame*
+nsLayoutUtils::FillAncestors(nsIFrame* aFrame,
+                             nsIFrame* aStopAtAncestor,
+                             nsTArray<nsIFrame*>* aAncestors)
+{
+  while (aFrame && aFrame != aStopAtAncestor) {
+    aAncestors->AppendElement(aFrame);
+    aFrame = nsLayoutUtils::GetParentOrPlaceholderFor(aFrame);
+  }
+  return aFrame;
+}
+
+// Return true if aFrame1 is after aFrame2
+static bool IsFrameAfter(nsIFrame* aFrame1, nsIFrame* aFrame2)
+{
+  nsIFrame* f = aFrame2;
+  do {
+    f = f->GetNextSibling();
+    if (f == aFrame1)
+      return true;
+  } while (f);
+  return false;
+}
+
+// static
+int32_t
+nsLayoutUtils::DoCompareTreePosition(nsIFrame* aFrame1,
+                                     nsIFrame* aFrame2,
+                                     int32_t aIf1Ancestor,
+                                     int32_t aIf2Ancestor,
+                                     nsIFrame* aCommonAncestor)
+{
+  NS_PRECONDITION(aFrame1, "aFrame1 must not be null");
+  NS_PRECONDITION(aFrame2, "aFrame2 must not be null");
+
+  AutoTArray<nsIFrame*,20> frame2Ancestors;
+  nsIFrame* nonCommonAncestor =
+    FillAncestors(aFrame2, aCommonAncestor, &frame2Ancestors);
+
+  return DoCompareTreePosition(aFrame1, aFrame2, frame2Ancestors,
+                               aIf1Ancestor, aIf2Ancestor,
+                               nonCommonAncestor ? aCommonAncestor : nullptr);
+}
+
+// static
+int32_t
+nsLayoutUtils::DoCompareTreePosition(nsIFrame* aFrame1,
+                                     nsIFrame* aFrame2,
+                                     nsTArray<nsIFrame*>& aFrame2Ancestors,
+                                     int32_t aIf1Ancestor,
+                                     int32_t aIf2Ancestor,
+                                     nsIFrame* aCommonAncestor)
+{
+  NS_PRECONDITION(aFrame1, "aFrame1 must not be null");
+  NS_PRECONDITION(aFrame2, "aFrame2 must not be null");
+
+  nsPresContext* presContext = aFrame1->PresContext();
+  if (presContext != aFrame2->PresContext()) {
+    NS_ERROR("no common ancestor at all, different documents");
+    return 0;
+  }
+
+  AutoTArray<nsIFrame*,20> frame1Ancestors;
+  if (aCommonAncestor &&
+      !FillAncestors(aFrame1, aCommonAncestor, &frame1Ancestors)) {
+    // We reached the root of the frame tree ... if aCommonAncestor was set,
+    // it is wrong
+    return DoCompareTreePosition(aFrame1, aFrame2,
+                                 aIf1Ancestor, aIf2Ancestor, nullptr);
+  }
+
+  int32_t last1 = int32_t(frame1Ancestors.Length()) - 1;
+  int32_t last2 = int32_t(aFrame2Ancestors.Length()) - 1;
+  while (last1 >= 0 && last2 >= 0 &&
+         frame1Ancestors[last1] == aFrame2Ancestors[last2]) {
+    last1--;
+    last2--;
+  }
+
+  if (last1 < 0) {
+    if (last2 < 0) {
+      NS_ASSERTION(aFrame1 == aFrame2, "internal error?");
+      return 0;
+    }
+    // aFrame1 is an ancestor of aFrame2
+    return aIf1Ancestor;
+  }
+
+  if (last2 < 0) {
+    // aFrame2 is an ancestor of aFrame1
+    return aIf2Ancestor;
+  }
+
+  nsIFrame* ancestor1 = frame1Ancestors[last1];
+  nsIFrame* ancestor2 = aFrame2Ancestors[last2];
+  // Now we should be able to walk sibling chains to find which one is first
+  if (IsFrameAfter(ancestor2, ancestor1))
+    return -1;
+  if (IsFrameAfter(ancestor1, ancestor2))
+    return 1;
+  NS_WARNING("Frames were in different child lists???");
+  return 0;
+}
+
+// static
+nsIFrame* nsLayoutUtils::GetLastSibling(nsIFrame* aFrame) {
+  if (!aFrame) {
+    return nullptr;
+  }
+
+  nsIFrame* next;
+  while ((next = aFrame->GetNextSibling()) != nullptr) {
+    aFrame = next;
+  }
+  return aFrame;
+}
+
+// static
+nsView*
+nsLayoutUtils::FindSiblingViewFor(nsView* aParentView, nsIFrame* aFrame) {
+  nsIFrame* parentViewFrame = aParentView->GetFrame();
+  nsIContent* parentViewContent = parentViewFrame ? parentViewFrame->GetContent() : nullptr;
+  for (nsView* insertBefore = aParentView->GetFirstChild(); insertBefore;
+       insertBefore = insertBefore->GetNextSibling()) {
+    nsIFrame* f = insertBefore->GetFrame();
+    if (!f) {
+      // this view could be some anonymous view attached to a meaningful parent
+      for (nsView* searchView = insertBefore->GetParent(); searchView;
+           searchView = searchView->GetParent()) {
+        f = searchView->GetFrame();
+        if (f) {
+          break;
+        }
+      }
+      NS_ASSERTION(f, "Can't find a frame anywhere!");
+    }
+    if (!f || !aFrame->GetContent() || !f->GetContent() ||
+        CompareTreePosition(aFrame->GetContent(), f->GetContent(), parentViewContent) > 0) {
+      // aFrame's content is after f's content (or we just don't know),
+      // so put our view before f's view
+      return insertBefore;
+    }
+  }
+  return nullptr;
+}
+
+//static
+nsIScrollableFrame*
+nsLayoutUtils::GetScrollableFrameFor(const nsIFrame *aScrolledFrame)
+{
+  nsIFrame *frame = aScrolledFrame->GetParent();
+  nsIScrollableFrame *sf = do_QueryFrame(frame);
+  return (sf && sf->GetScrolledFrame() == aScrolledFrame) ? sf : nullptr;
+}
+
+/* static */ void
+nsLayoutUtils::SetFixedPositionLayerData(Layer* aLayer,
+                                         const nsIFrame* aViewportFrame,
+                                         const nsRect& aAnchorRect,
+                                         const nsIFrame* aFixedPosFrame,
+                                         nsPresContext* aPresContext,
+                                         const ContainerLayerParameters& aContainerParameters) {
+  // Find out the rect of the viewport frame relative to the reference frame.
+  // This, in conjunction with the container scale, will correspond to the
+  // coordinate-space of the built layer.
+  float factor = aPresContext->AppUnitsPerDevPixel();
+  Rect anchorRect(NSAppUnitsToFloatPixels(aAnchorRect.x, factor) *
+                    aContainerParameters.mXScale,
+                  NSAppUnitsToFloatPixels(aAnchorRect.y, factor) *
+                    aContainerParameters.mYScale,
+                  NSAppUnitsToFloatPixels(aAnchorRect.width, factor) *
+                    aContainerParameters.mXScale,
+                  NSAppUnitsToFloatPixels(aAnchorRect.height, factor) *
+                    aContainerParameters.mYScale);
+  // Need to transform anchorRect from the container layer's coordinate system
+  // into aLayer's coordinate system.
+  Matrix transform2d;
+  if (aLayer->GetTransform().Is2D(&transform2d)) {
+    transform2d.Invert();
+    anchorRect = transform2d.TransformBounds(anchorRect);
+  } else {
+    NS_ERROR("3D transform found between fixedpos content and its viewport (should never happen)");
+    anchorRect = Rect(0,0,0,0);
+  }
+
+  // Work out the anchor point for this fixed position layer. We assume that
+  // any positioning set (left/top/right/bottom) indicates that the
+  // corresponding side of its container should be the anchor point,
+  // defaulting to top-left.
+  LayerPoint anchor(anchorRect.x, anchorRect.y);
+
+  int32_t sides = eSideBitsNone;
+  if (aFixedPosFrame != aViewportFrame) {
+    const nsStylePosition* position = aFixedPosFrame->StylePosition();
+    if (position->mOffset.GetRightUnit() != eStyleUnit_Auto) {
+      sides |= eSideBitsRight;
+      if (position->mOffset.GetLeftUnit() != eStyleUnit_Auto) {
+        sides |= eSideBitsLeft;
+        anchor.x = anchorRect.x + anchorRect.width / 2.f;
+      } else {
+        anchor.x = anchorRect.XMost();
+      }
+    }
+    if (position->mOffset.GetBottomUnit() != eStyleUnit_Auto) {
+      sides |= eSideBitsBottom;
+      if (position->mOffset.GetTopUnit() != eStyleUnit_Auto) {
+        sides |= eSideBitsTop;
+        anchor.y = anchorRect.y + anchorRect.height / 2.f;
+      } else {
+        anchor.y = anchorRect.YMost();
+      }
+    }
+  }
+
+  ViewID id = FrameMetrics::NULL_SCROLL_ID;
+  if (nsIFrame* rootScrollFrame = aPresContext->PresShell()->GetRootScrollFrame()) {
+    if (nsIContent* content = rootScrollFrame->GetContent()) {
+      id = FindOrCreateIDFor(content);
+    }
+  }
+  aLayer->SetFixedPositionData(id, anchor, sides);
+}
+
+bool
+nsLayoutUtils::ViewportHasDisplayPort(nsPresContext* aPresContext)
+{
+  nsIFrame* rootScrollFrame =
+    aPresContext->PresShell()->GetRootScrollFrame();
+  return rootScrollFrame &&
+    nsLayoutUtils::HasDisplayPort(rootScrollFrame->GetContent());
+}
+
+bool
+nsLayoutUtils::IsFixedPosFrameInDisplayPort(const nsIFrame* aFrame)
+{
+  // Fixed-pos frames are parented by the viewport frame or the page content frame.
+  // We'll assume that printing/print preview don't have displayports for their
+  // pages!
+  nsIFrame* parent = aFrame->GetParent();
+  if (!parent || parent->GetParent() ||
+      aFrame->StyleDisplay()->mPosition != NS_STYLE_POSITION_FIXED) {
+    return false;
+  }
+  return ViewportHasDisplayPort(aFrame->PresContext());
+}
+
+NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(ScrollbarThumbLayerized, bool)
+
+/* static */ void
+nsLayoutUtils::SetScrollbarThumbLayerization(nsIFrame* aThumbFrame, bool aLayerize)
+{
+  aThumbFrame->Properties().Set(ScrollbarThumbLayerized(), aLayerize);
+}
+
+bool
+nsLayoutUtils::IsScrollbarThumbLayerized(nsIFrame* aThumbFrame)
+{
+  return aThumbFrame->Properties().Get(ScrollbarThumbLayerized());
+}
+
+// static
+nsIScrollableFrame*
+nsLayoutUtils::GetNearestScrollableFrameForDirection(nsIFrame* aFrame,
+                                                     Direction aDirection)
+{
+  NS_ASSERTION(aFrame, "GetNearestScrollableFrameForDirection expects a non-null frame");
+  for (nsIFrame* f = aFrame; f; f = nsLayoutUtils::GetCrossDocParentFrame(f)) {
+    nsIScrollableFrame* scrollableFrame = do_QueryFrame(f);
+    if (scrollableFrame) {
+      ScrollbarStyles ss = scrollableFrame->GetScrollbarStyles();
+      uint32_t directions = scrollableFrame->GetPerceivedScrollingDirections();
+      if (aDirection == eVertical ?
+          (ss.mVertical != NS_STYLE_OVERFLOW_HIDDEN &&
+           (directions & nsIScrollableFrame::VERTICAL)) :
+          (ss.mHorizontal != NS_STYLE_OVERFLOW_HIDDEN &&
+           (directions & nsIScrollableFrame::HORIZONTAL)))
+        return scrollableFrame;
+    }
+  }
+  return nullptr;
+}
+
+// static
+nsIScrollableFrame*
+nsLayoutUtils::GetNearestScrollableFrame(nsIFrame* aFrame, uint32_t aFlags)
+{
+  NS_ASSERTION(aFrame, "GetNearestScrollableFrame expects a non-null frame");
+  for (nsIFrame* f = aFrame; f; f = (aFlags & SCROLLABLE_SAME_DOC) ?
+       f->GetParent() : nsLayoutUtils::GetCrossDocParentFrame(f)) {
+    nsIScrollableFrame* scrollableFrame = do_QueryFrame(f);
+    if (scrollableFrame) {
+      if (aFlags & SCROLLABLE_ONLY_ASYNC_SCROLLABLE) {
+        if (scrollableFrame->WantAsyncScroll()) {
+          return scrollableFrame;
+        }
+      } else {
+        ScrollbarStyles ss = scrollableFrame->GetScrollbarStyles();
+        if ((aFlags & SCROLLABLE_INCLUDE_HIDDEN) ||
+            ss.mVertical != NS_STYLE_OVERFLOW_HIDDEN ||
+            ss.mHorizontal != NS_STYLE_OVERFLOW_HIDDEN) {
+          return scrollableFrame;
+        }
+      }
+      if (aFlags & SCROLLABLE_ALWAYS_MATCH_ROOT) {
+        nsIPresShell* ps = f->PresContext()->PresShell();
+        if (ps->GetRootScrollFrame() == f &&
+            ps->GetDocument() && ps->GetDocument()->IsRootDisplayDocument()) {
+          return scrollableFrame;
+        }
+      }
+    }
+    if ((aFlags & SCROLLABLE_FIXEDPOS_FINDS_ROOT) &&
+        f->StyleDisplay()->mPosition == NS_STYLE_POSITION_FIXED &&
+        nsLayoutUtils::IsReallyFixedPos(f)) {
+      return f->PresContext()->PresShell()->GetRootScrollFrameAsScrollable();
+    }
+  }
+  return nullptr;
+}
+
+// static
+nsRect
+nsLayoutUtils::GetScrolledRect(nsIFrame* aScrolledFrame,
+                               const nsRect& aScrolledFrameOverflowArea,
+                               const nsSize& aScrollPortSize,
+                               uint8_t aDirection)
+{
+  WritingMode wm = aScrolledFrame->GetWritingMode();
+  // Potentially override the frame's direction to use the direction found
+  // by ScrollFrameHelper::GetScrolledFrameDir()
+  wm.SetDirectionFromBidiLevel(aDirection == NS_STYLE_DIRECTION_RTL ? 1 : 0);
+
+  nscoord x1 = aScrolledFrameOverflowArea.x,
+          x2 = aScrolledFrameOverflowArea.XMost(),
+          y1 = aScrolledFrameOverflowArea.y,
+          y2 = aScrolledFrameOverflowArea.YMost();
+
+  bool horizontal = !wm.IsVertical();
+
+  // Clamp the horizontal start-edge (x1 or x2, depending whether the logical
+  // axis that corresponds to horizontal progresses from L-R or R-L).
+  // In horizontal writing mode, we need to check IsInlineReversed() to see
+  // which side to clamp; in vertical mode, it depends on the block direction.
+  if ((horizontal && !wm.IsInlineReversed()) || wm.IsVerticalLR()) {
+    if (x1 < 0) {
+      x1 = 0;
+    }
+  } else {
+    if (x2 > aScrollPortSize.width) {
+      x2 = aScrollPortSize.width;
+    }
+    // When the scrolled frame chooses a size larger than its available width
+    // (because its padding alone is larger than the available width), we need
+    // to keep the start-edge of the scroll frame anchored to the start-edge of
+    // the scrollport.
+    // When the scrolled frame is RTL, this means moving it in our left-based
+    // coordinate system, so we need to compensate for its extra width here by
+    // effectively repositioning the frame.
+    nscoord extraWidth =
+      std::max(0, aScrolledFrame->GetSize().width - aScrollPortSize.width);
+    x2 += extraWidth;
+  }
+
+  // Similarly, clamp the vertical start-edge.
+  // In horizontal writing mode, the block direction is always top-to-bottom;
+  // in vertical writing mode, we need to check IsInlineReversed().
+  if (horizontal || !wm.IsInlineReversed()) {
+    if (y1 < 0) {
+      y1 = 0;
+    }
+  } else {
+    if (y2 > aScrollPortSize.height) {
+      y2 = aScrollPortSize.height;
+    }
+    nscoord extraHeight =
+      std::max(0, aScrolledFrame->GetSize().height - aScrollPortSize.height);
+    y2 += extraHeight;
+  }
+
+  return nsRect(x1, y1, x2 - x1, y2 - y1);
+}
+
+//static
+bool
+nsLayoutUtils::HasPseudoStyle(nsIContent* aContent,
+                              nsStyleContext* aStyleContext,
+                              CSSPseudoElementType aPseudoElement,
+                              nsPresContext* aPresContext)
+{
+  NS_PRECONDITION(aPresContext, "Must have a prescontext");
+
+  RefPtr<nsStyleContext> pseudoContext;
+  if (aContent) {
+    pseudoContext = aPresContext->StyleSet()->
+      ProbePseudoElementStyle(aContent->AsElement(), aPseudoElement,
+                              aStyleContext);
+  }
+  return pseudoContext != nullptr;
+}
+
+nsPoint
+nsLayoutUtils::GetDOMEventCoordinatesRelativeTo(nsIDOMEvent* aDOMEvent, nsIFrame* aFrame)
+{
+  if (!aDOMEvent)
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  WidgetEvent* event = aDOMEvent->WidgetEventPtr();
+  if (!event)
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  return GetEventCoordinatesRelativeTo(event, aFrame);
+}
+
+nsPoint
+nsLayoutUtils::GetEventCoordinatesRelativeTo(const WidgetEvent* aEvent,
+                                             nsIFrame* aFrame)
+{
+  if (!aEvent || (aEvent->mClass != eMouseEventClass &&
+                  aEvent->mClass != eMouseScrollEventClass &&
+                  aEvent->mClass != eWheelEventClass &&
+                  aEvent->mClass != eDragEventClass &&
+                  aEvent->mClass != eSimpleGestureEventClass &&
+                  aEvent->mClass != ePointerEventClass &&
+                  aEvent->mClass != eGestureNotifyEventClass &&
+                  aEvent->mClass != eTouchEventClass &&
+                  aEvent->mClass != eQueryContentEventClass))
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+
+  return GetEventCoordinatesRelativeTo(aEvent,
+           aEvent->AsGUIEvent()->mRefPoint,
+           aFrame);
+}
+
+nsPoint
+nsLayoutUtils::GetEventCoordinatesRelativeTo(const WidgetEvent* aEvent,
+                                             const LayoutDeviceIntPoint& aPoint,
+                                             nsIFrame* aFrame)
+{
+  if (!aFrame) {
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  }
+
+  nsIWidget* widget = aEvent->AsGUIEvent()->mWidget;
+  if (!widget) {
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  }
+
+  return GetEventCoordinatesRelativeTo(widget, aPoint, aFrame);
+}
+
+nsPoint
+nsLayoutUtils::GetEventCoordinatesRelativeTo(nsIWidget* aWidget,
+                                             const LayoutDeviceIntPoint& aPoint,
+                                             nsIFrame* aFrame)
+{
+  if (!aFrame || !aWidget) {
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  }
+
+  nsView* view = aFrame->GetView();
+  if (view) {
+    nsIWidget* frameWidget = view->GetWidget();
+    if (frameWidget && frameWidget == aWidget) {
+      // Special case this cause it happens a lot.
+      // This also fixes bug 664707, events in the extra-special case of select
+      // dropdown popups that are transformed.
+      nsPresContext* presContext = aFrame->PresContext();
+      nsPoint pt(presContext->DevPixelsToAppUnits(aPoint.x),
+                 presContext->DevPixelsToAppUnits(aPoint.y));
+      pt = pt - view->ViewToWidgetOffset();
+      pt = pt.RemoveResolution(GetCurrentAPZResolutionScale(presContext->PresShell()));
+      return pt;
+    }
+  }
+
+  /* If we walk up the frame tree and discover that any of the frames are
+   * transformed, we need to do extra work to convert from the global
+   * space to the local space.
+   */
+  nsIFrame* rootFrame = aFrame;
+  bool transformFound = false;
+  for (nsIFrame* f = aFrame; f; f = GetCrossDocParentFrame(f)) {
+    if (f->IsTransformed()) {
+      transformFound = true;
+    }
+
+    rootFrame = f;
+  }
+
+  nsView* rootView = rootFrame->GetView();
+  if (!rootView) {
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  }
+
+  nsPoint widgetToView = TranslateWidgetToView(rootFrame->PresContext(),
+                                               aWidget, aPoint, rootView);
+
+  if (widgetToView == nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE)) {
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  }
+
+  // Convert from root document app units to app units of the document aFrame
+  // is in.
+  int32_t rootAPD = rootFrame->PresContext()->AppUnitsPerDevPixel();
+  int32_t localAPD = aFrame->PresContext()->AppUnitsPerDevPixel();
+  widgetToView = widgetToView.ScaleToOtherAppUnits(rootAPD, localAPD);
+  nsIPresShell* shell = aFrame->PresContext()->PresShell();
+
+  // XXX Bug 1224748 - Update nsLayoutUtils functions to correctly handle nsPresShell resolution
+  widgetToView = widgetToView.RemoveResolution(GetCurrentAPZResolutionScale(shell));
+
+  /* If we encountered a transform, we can't do simple arithmetic to figure
+   * out how to convert back to aFrame's coordinates and must use the CTM.
+   */
+  if (transformFound || aFrame->IsSVGText()) {
+    return TransformRootPointToFrame(aFrame, widgetToView);
+  }
+
+  /* Otherwise, all coordinate systems are translations of one another,
+   * so we can just subtract out the difference.
+   */
+  return widgetToView - aFrame->GetOffsetToCrossDoc(rootFrame);
+}
+
+nsIFrame*
+nsLayoutUtils::GetPopupFrameForEventCoordinates(nsPresContext* aPresContext,
+                                                const WidgetEvent* aEvent)
+{
+#ifdef MOZ_XUL
+  nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
+  if (!pm) {
+    return nullptr;
+  }
+  nsTArray<nsIFrame*> popups;
+  pm->GetVisiblePopups(popups);
+  uint32_t i;
+  // Search from top to bottom
+  for (i = 0; i < popups.Length(); i++) {
+    nsIFrame* popup = popups[i];
+    if (popup->PresContext()->GetRootPresContext() == aPresContext &&
+        popup->GetScrollableOverflowRect().Contains(
+          GetEventCoordinatesRelativeTo(aEvent, popup))) {
+      return popup;
+    }
+  }
+#endif
+  return nullptr;
+}
+
+static void ConstrainToCoordValues(float& aStart, float& aSize)
+{
+  MOZ_ASSERT(aSize >= 0);
+
+  // Here we try to make sure that the resulting nsRect will continue to cover
+  // as much of the area that was covered by the original gfx Rect as possible.
+
+  // We clamp the bounds of the rect to {nscoord_MIN,nscoord_MAX} since
+  // nsRect::X/Y() and nsRect::XMost/YMost() can't return values outwith this
+  // range:
+  float end = aStart + aSize;
+  aStart = clamped(aStart, float(nscoord_MIN), float(nscoord_MAX));
+  end = clamped(end, float(nscoord_MIN), float(nscoord_MAX));
+
+  aSize = end - aStart;
+
+  // We must also clamp aSize to {0,nscoord_MAX} since nsRect::Width/Height()
+  // can't return a value greater than nscoord_MAX. If aSize is greater than
+  // nscoord_MAX then we reduce it to nscoord_MAX while keeping the rect
+  // centered:
+  if (aSize > nscoord_MAX) {
+    float excess = aSize - nscoord_MAX;
+    excess /= 2;
+    aStart += excess;
+    aSize = nscoord_MAX;
+  }
+}
+
+/**
+ * Given a gfxFloat, constrains its value to be between nscoord_MIN and nscoord_MAX.
+ *
+ * @param aVal The value to constrain (in/out)
+ */
+static void ConstrainToCoordValues(gfxFloat& aVal)
+{
+  if (aVal <= nscoord_MIN)
+    aVal = nscoord_MIN;
+  else if (aVal >= nscoord_MAX)
+    aVal = nscoord_MAX;
+}
+
+static void ConstrainToCoordValues(gfxFloat& aStart, gfxFloat& aSize)
+{
+  gfxFloat max = aStart + aSize;
+
+  // Clamp the end points to within nscoord range
+  ConstrainToCoordValues(aStart);
+  ConstrainToCoordValues(max);
+
+  aSize = max - aStart;
+  // If the width if still greater than the max nscoord, then bring both
+  // endpoints in by the same amount until it fits.
+  if (aSize > nscoord_MAX) {
+    gfxFloat excess = aSize - nscoord_MAX;
+    excess /= 2;
+
+    aStart += excess;
+    aSize = nscoord_MAX;
+  } else if (aSize < nscoord_MIN) {
+    gfxFloat excess = aSize - nscoord_MIN;
+    excess /= 2;
+
+    aStart -= excess;
+    aSize = nscoord_MIN;
+  }
+}
+
+nsRect
+nsLayoutUtils::RoundGfxRectToAppRect(const Rect &aRect, float aFactor)
+{
+  /* Get a new Rect whose units are app units by scaling by the specified factor. */
+  Rect scaledRect = aRect;
+  scaledRect.ScaleRoundOut(aFactor);
+
+  /* We now need to constrain our results to the max and min values for coords. */
+  ConstrainToCoordValues(scaledRect.x, scaledRect.width);
+  ConstrainToCoordValues(scaledRect.y, scaledRect.height);
+
+  /* Now typecast everything back.  This is guaranteed to be safe. */
+  return nsRect(nscoord(scaledRect.X()), nscoord(scaledRect.Y()),
+                nscoord(scaledRect.Width()), nscoord(scaledRect.Height()));
+}
+
+nsRect
+nsLayoutUtils::RoundGfxRectToAppRect(const gfxRect &aRect, float aFactor)
+{
+  /* Get a new gfxRect whose units are app units by scaling by the specified factor. */
+  gfxRect scaledRect = aRect;
+  scaledRect.ScaleRoundOut(aFactor);
+
+  /* We now need to constrain our results to the max and min values for coords. */
+  ConstrainToCoordValues(scaledRect.x, scaledRect.width);
+  ConstrainToCoordValues(scaledRect.y, scaledRect.height);
+
+  /* Now typecast everything back.  This is guaranteed to be safe. */
+  return nsRect(nscoord(scaledRect.X()), nscoord(scaledRect.Y()),
+                nscoord(scaledRect.Width()), nscoord(scaledRect.Height()));
+}
+
+
+nsRegion
+nsLayoutUtils::RoundedRectIntersectRect(const nsRect& aRoundedRect,
+                                        const nscoord aRadii[8],
+                                        const nsRect& aContainedRect)
+{
+  // rectFullHeight and rectFullWidth together will approximately contain
+  // the total area of the frame minus the rounded corners.
+  nsRect rectFullHeight = aRoundedRect;
+  nscoord xDiff = std::max(aRadii[NS_CORNER_TOP_LEFT_X], aRadii[NS_CORNER_BOTTOM_LEFT_X]);
+  rectFullHeight.x += xDiff;
+  rectFullHeight.width -= std::max(aRadii[NS_CORNER_TOP_RIGHT_X],
+                                 aRadii[NS_CORNER_BOTTOM_RIGHT_X]) + xDiff;
+  nsRect r1;
+  r1.IntersectRect(rectFullHeight, aContainedRect);
+
+  nsRect rectFullWidth = aRoundedRect;
+  nscoord yDiff = std::max(aRadii[NS_CORNER_TOP_LEFT_Y], aRadii[NS_CORNER_TOP_RIGHT_Y]);
+  rectFullWidth.y += yDiff;
+  rectFullWidth.height -= std::max(aRadii[NS_CORNER_BOTTOM_LEFT_Y],
+                                 aRadii[NS_CORNER_BOTTOM_RIGHT_Y]) + yDiff;
+  nsRect r2;
+  r2.IntersectRect(rectFullWidth, aContainedRect);
+
+  nsRegion result;
+  result.Or(r1, r2);
+  return result;
+}
+
+nsIntRegion
+nsLayoutUtils::RoundedRectIntersectIntRect(const nsIntRect& aRoundedRect,
+                                           const RectCornerRadii& aCornerRadii,
+                                           const nsIntRect& aContainedRect)
+{
+  // rectFullHeight and rectFullWidth together will approximately contain
+  // the total area of the frame minus the rounded corners.
+  nsIntRect rectFullHeight = aRoundedRect;
+  uint32_t xDiff = std::max(aCornerRadii.TopLeft().width,
+                            aCornerRadii.BottomLeft().width);
+  rectFullHeight.x += xDiff;
+  rectFullHeight.width -= std::max(aCornerRadii.TopRight().width,
+                                   aCornerRadii.BottomRight().width) + xDiff;
+  nsIntRect r1;
+  r1.IntersectRect(rectFullHeight, aContainedRect);
+
+  nsIntRect rectFullWidth = aRoundedRect;
+  uint32_t yDiff = std::max(aCornerRadii.TopLeft().height,
+                            aCornerRadii.TopRight().height);
+  rectFullWidth.y += yDiff;
+  rectFullWidth.height -= std::max(aCornerRadii.BottomLeft().height,
+                                   aCornerRadii.BottomRight().height) + yDiff;
+  nsIntRect r2;
+  r2.IntersectRect(rectFullWidth, aContainedRect);
+
+  nsIntRegion result;
+  result.Or(r1, r2);
+  return result;
+}
+
+// Helper for RoundedRectIntersectsRect.
+static bool
+CheckCorner(nscoord aXOffset, nscoord aYOffset,
+            nscoord aXRadius, nscoord aYRadius)
+{
+  MOZ_ASSERT(aXOffset > 0 && aYOffset > 0,
+             "must not pass nonpositives to CheckCorner");
+  MOZ_ASSERT(aXRadius >= 0 && aYRadius >= 0,
+             "must not pass negatives to CheckCorner");
+
+  // Avoid floating point math unless we're either (1) within the
+  // quarter-ellipse area at the rounded corner or (2) outside the
+  // rounding.
+  if (aXOffset >= aXRadius || aYOffset >= aYRadius)
+    return true;
+
+  // Convert coordinates to a unit circle with (0,0) as the center of
+  // curvature, and see if we're inside the circle or outside.
+  float scaledX = float(aXRadius - aXOffset) / float(aXRadius);
+  float scaledY = float(aYRadius - aYOffset) / float(aYRadius);
+  return scaledX * scaledX + scaledY * scaledY < 1.0f;
+}
+
+bool
+nsLayoutUtils::RoundedRectIntersectsRect(const nsRect& aRoundedRect,
+                                         const nscoord aRadii[8],
+                                         const nsRect& aTestRect)
+{
+  if (!aTestRect.Intersects(aRoundedRect))
+    return false;
+
+  // distances from this edge of aRoundedRect to opposite edge of aTestRect,
+  // which we know are positive due to the Intersects check above.
+  nsMargin insets;
+  insets.top = aTestRect.YMost() - aRoundedRect.y;
+  insets.right = aRoundedRect.XMost() - aTestRect.x;
+  insets.bottom = aRoundedRect.YMost() - aTestRect.y;
+  insets.left = aTestRect.XMost() - aRoundedRect.x;
+
+  // Check whether the bottom-right corner of aTestRect is inside the
+  // top left corner of aBounds when rounded by aRadii, etc.  If any
+  // corner is not, then fail; otherwise succeed.
+  return CheckCorner(insets.left, insets.top,
+                     aRadii[NS_CORNER_TOP_LEFT_X],
+                     aRadii[NS_CORNER_TOP_LEFT_Y]) &&
+         CheckCorner(insets.right, insets.top,
+                     aRadii[NS_CORNER_TOP_RIGHT_X],
+                     aRadii[NS_CORNER_TOP_RIGHT_Y]) &&
+         CheckCorner(insets.right, insets.bottom,
+                     aRadii[NS_CORNER_BOTTOM_RIGHT_X],
+                     aRadii[NS_CORNER_BOTTOM_RIGHT_Y]) &&
+         CheckCorner(insets.left, insets.bottom,
+                     aRadii[NS_CORNER_BOTTOM_LEFT_X],
+                     aRadii[NS_CORNER_BOTTOM_LEFT_Y]);
+}
+
+nsRect
+nsLayoutUtils::MatrixTransformRect(const nsRect &aBounds,
+                                   const Matrix4x4 &aMatrix, float aFactor)
+{
+  RectDouble image = RectDouble(NSAppUnitsToDoublePixels(aBounds.x, aFactor),
+                                NSAppUnitsToDoublePixels(aBounds.y, aFactor),
+                                NSAppUnitsToDoublePixels(aBounds.width, aFactor),
+                                NSAppUnitsToDoublePixels(aBounds.height, aFactor));
+
+  RectDouble maxBounds = RectDouble(double(nscoord_MIN) / aFactor * 0.5,
+                                    double(nscoord_MIN) / aFactor * 0.5,
+                                    double(nscoord_MAX) / aFactor,
+                                    double(nscoord_MAX) / aFactor);
+
+  image = aMatrix.TransformAndClipBounds(image, maxBounds);
+
+  return RoundGfxRectToAppRect(ThebesRect(image), aFactor);
+}
+
+nsPoint
+nsLayoutUtils::MatrixTransformPoint(const nsPoint &aPoint,
+                                    const Matrix4x4 &aMatrix, float aFactor)
+{
+  gfxPoint image = gfxPoint(NSAppUnitsToFloatPixels(aPoint.x, aFactor),
+                            NSAppUnitsToFloatPixels(aPoint.y, aFactor));
+  image.Transform(aMatrix);
+  return nsPoint(NSFloatPixelsToAppUnits(float(image.x), aFactor),
+                 NSFloatPixelsToAppUnits(float(image.y), aFactor));
+}
+
+void
+nsLayoutUtils::PostTranslate(Matrix4x4& aTransform, const nsPoint& aOrigin, float aAppUnitsPerPixel, bool aRounded)
+{
+  Point3D gfxOrigin =
+    Point3D(NSAppUnitsToFloatPixels(aOrigin.x, aAppUnitsPerPixel),
+            NSAppUnitsToFloatPixels(aOrigin.y, aAppUnitsPerPixel),
+            0.0f);
+  if (aRounded) {
+    gfxOrigin.x = NS_round(gfxOrigin.x);
+    gfxOrigin.y = NS_round(gfxOrigin.y);
+  }
+  aTransform.PostTranslate(gfxOrigin);
+}
+
+Matrix4x4
+nsLayoutUtils::GetTransformToAncestor(nsIFrame *aFrame, const nsIFrame *aAncestor)
+{
+  nsIFrame* parent;
+  Matrix4x4 ctm;
+  if (aFrame == aAncestor) {
+    return ctm;
+  }
+  ctm = aFrame->GetTransformMatrix(aAncestor, &parent);
+  while (parent && parent != aAncestor) {
+    if (!parent->Extend3DContext()) {
+      ctm.ProjectTo2D();
+    }
+    ctm = ctm * parent->GetTransformMatrix(aAncestor, &parent);
+  }
+  return ctm;
+}
+
+gfxSize
+nsLayoutUtils::GetTransformToAncestorScale(nsIFrame* aFrame)
+{
+  Matrix4x4 transform = GetTransformToAncestor(aFrame,
+      nsLayoutUtils::GetDisplayRootFrame(aFrame));
+  Matrix transform2D;
+  if (transform.Is2D(&transform2D)) {
+    return ThebesMatrix(transform2D).ScaleFactors(true);
+  }
+  return gfxSize(1, 1);
+}
+
+static Matrix4x4
+GetTransformToAncestorExcludingAnimated(nsIFrame* aFrame,
+                                        const nsIFrame* aAncestor)
+{
+  nsIFrame* parent;
+  Matrix4x4 ctm;
+  if (aFrame == aAncestor) {
+    return ctm;
+  }
+  if (ActiveLayerTracker::IsScaleSubjectToAnimation(aFrame)) {
+    return ctm;
+  }
+  ctm = aFrame->GetTransformMatrix(aAncestor, &parent);
+  while (parent && parent != aAncestor) {
+    if (ActiveLayerTracker::IsScaleSubjectToAnimation(parent)) {
+      return Matrix4x4();
+    }
+    if (!parent->Extend3DContext()) {
+      ctm.ProjectTo2D();
+    }
+    ctm = ctm * parent->GetTransformMatrix(aAncestor, &parent);
+  }
+  return ctm;
+}
+
+gfxSize
+nsLayoutUtils::GetTransformToAncestorScaleExcludingAnimated(nsIFrame* aFrame)
+{
+  Matrix4x4 transform = GetTransformToAncestorExcludingAnimated(aFrame,
+      nsLayoutUtils::GetDisplayRootFrame(aFrame));
+  Matrix transform2D;
+  if (transform.Is2D(&transform2D)) {
+    return ThebesMatrix(transform2D).ScaleFactors(true);
+  }
+  return gfxSize(1, 1);
+}
+
+nsIFrame*
+nsLayoutUtils::FindNearestCommonAncestorFrame(nsIFrame* aFrame1, nsIFrame* aFrame2)
+{
+  AutoTArray<nsIFrame*,100> ancestors1;
+  AutoTArray<nsIFrame*,100> ancestors2;
+  nsIFrame* commonAncestor = nullptr;
+  if (aFrame1->PresContext() == aFrame2->PresContext()) {
+    commonAncestor = aFrame1->PresContext()->PresShell()->GetRootFrame();
+  }
+  for (nsIFrame* f = aFrame1; f != commonAncestor;
+       f = nsLayoutUtils::GetCrossDocParentFrame(f)) {
+    ancestors1.AppendElement(f);
+  }
+  for (nsIFrame* f = aFrame2; f != commonAncestor;
+       f = nsLayoutUtils::GetCrossDocParentFrame(f)) {
+    ancestors2.AppendElement(f);
+  }
+  uint32_t minLengths = std::min(ancestors1.Length(), ancestors2.Length());
+  for (uint32_t i = 1; i <= minLengths; ++i) {
+    if (ancestors1[ancestors1.Length() - i] == ancestors2[ancestors2.Length() - i]) {
+      commonAncestor = ancestors1[ancestors1.Length() - i];
+    } else {
+      break;
+    }
+  }
+  return commonAncestor;
+}
+
+nsLayoutUtils::TransformResult
+nsLayoutUtils::TransformPoints(nsIFrame* aFromFrame, nsIFrame* aToFrame,
+                               uint32_t aPointCount, CSSPoint* aPoints)
+{
+  nsIFrame* nearestCommonAncestor = FindNearestCommonAncestorFrame(aFromFrame, aToFrame);
+  if (!nearestCommonAncestor) {
+    return NO_COMMON_ANCESTOR;
+  }
+  Matrix4x4 downToDest = GetTransformToAncestor(aToFrame, nearestCommonAncestor);
+  if (downToDest.IsSingular()) {
+    return NONINVERTIBLE_TRANSFORM;
+  }
+  downToDest.Invert();
+  Matrix4x4 upToAncestor = GetTransformToAncestor(aFromFrame, nearestCommonAncestor);
+  CSSToLayoutDeviceScale devPixelsPerCSSPixelFromFrame =
+      aFromFrame->PresContext()->CSSToDevPixelScale();
+  CSSToLayoutDeviceScale devPixelsPerCSSPixelToFrame =
+      aToFrame->PresContext()->CSSToDevPixelScale();
+  for (uint32_t i = 0; i < aPointCount; ++i) {
+    LayoutDevicePoint devPixels = aPoints[i] * devPixelsPerCSSPixelFromFrame;
+    // What should the behaviour be if some of the points aren't invertible
+    // and others are? Just assume all points are for now.
+    Point toDevPixels = downToDest.ProjectPoint(
+        (upToAncestor.TransformPoint(Point(devPixels.x, devPixels.y)))).As2DPoint();
+    // Divide here so that when the devPixelsPerCSSPixels are the same, we get the correct
+    // answer instead of some inaccuracy multiplying a number by its reciprocal.
+    aPoints[i] = LayoutDevicePoint(toDevPixels.x, toDevPixels.y) /
+        devPixelsPerCSSPixelToFrame;
+  }
+  return TRANSFORM_SUCCEEDED;
+}
+
+nsLayoutUtils::TransformResult
+nsLayoutUtils::TransformPoint(nsIFrame* aFromFrame, nsIFrame* aToFrame,
+                              nsPoint& aPoint)
+{
+  nsIFrame* nearestCommonAncestor = FindNearestCommonAncestorFrame(aFromFrame, aToFrame);
+  if (!nearestCommonAncestor) {
+    return NO_COMMON_ANCESTOR;
+  }
+  Matrix4x4 downToDest = GetTransformToAncestor(aToFrame, nearestCommonAncestor);
+  if (downToDest.IsSingular()) {
+    return NONINVERTIBLE_TRANSFORM;
+  }
+  downToDest.Invert();
+  Matrix4x4 upToAncestor = GetTransformToAncestor(aFromFrame, nearestCommonAncestor);
+
+  float devPixelsPerAppUnitFromFrame =
+    1.0f / aFromFrame->PresContext()->AppUnitsPerDevPixel();
+  float devPixelsPerAppUnitToFrame =
+    1.0f / aToFrame->PresContext()->AppUnitsPerDevPixel();
+  Point4D toDevPixels = downToDest.ProjectPoint(
+      upToAncestor.TransformPoint(Point(aPoint.x * devPixelsPerAppUnitFromFrame,
+                                        aPoint.y * devPixelsPerAppUnitFromFrame)));
+  if (!toDevPixels.HasPositiveWCoord()) {
+    // Not strictly true, but we failed to get a valid point in this
+    // coordinate space.
+    return NONINVERTIBLE_TRANSFORM;
+  }
+  aPoint.x = NSToCoordRound(toDevPixels.x / devPixelsPerAppUnitToFrame);
+  aPoint.y = NSToCoordRound(toDevPixels.y / devPixelsPerAppUnitToFrame);
+  return TRANSFORM_SUCCEEDED;
+}
+
+nsLayoutUtils::TransformResult
+nsLayoutUtils::TransformRect(nsIFrame* aFromFrame, nsIFrame* aToFrame,
+                             nsRect& aRect)
+{
+  nsIFrame* nearestCommonAncestor = FindNearestCommonAncestorFrame(aFromFrame, aToFrame);
+  if (!nearestCommonAncestor) {
+    return NO_COMMON_ANCESTOR;
+  }
+  Matrix4x4 downToDest = GetTransformToAncestor(aToFrame, nearestCommonAncestor);
+  if (downToDest.IsSingular()) {
+    return NONINVERTIBLE_TRANSFORM;
+  }
+  downToDest.Invert();
+  Matrix4x4 upToAncestor = GetTransformToAncestor(aFromFrame, nearestCommonAncestor);
+
+  float devPixelsPerAppUnitFromFrame =
+    1.0f / aFromFrame->PresContext()->AppUnitsPerDevPixel();
+  float devPixelsPerAppUnitToFrame =
+    1.0f / aToFrame->PresContext()->AppUnitsPerDevPixel();
+  gfx::Rect toDevPixels = downToDest.ProjectRectBounds(
+    upToAncestor.ProjectRectBounds(
+      gfx::Rect(aRect.x * devPixelsPerAppUnitFromFrame,
+                aRect.y * devPixelsPerAppUnitFromFrame,
+                aRect.width * devPixelsPerAppUnitFromFrame,
+                aRect.height * devPixelsPerAppUnitFromFrame),
+      Rect(-std::numeric_limits<Float>::max() * 0.5f,
+           -std::numeric_limits<Float>::max() * 0.5f,
+           std::numeric_limits<Float>::max(),
+           std::numeric_limits<Float>::max())),
+    Rect(-std::numeric_limits<Float>::max() * devPixelsPerAppUnitFromFrame * 0.5f,
+         -std::numeric_limits<Float>::max() * devPixelsPerAppUnitFromFrame * 0.5f,
+         std::numeric_limits<Float>::max() * devPixelsPerAppUnitFromFrame,
+         std::numeric_limits<Float>::max() * devPixelsPerAppUnitFromFrame));
+  aRect.x = toDevPixels.x / devPixelsPerAppUnitToFrame;
+  aRect.y = toDevPixels.y / devPixelsPerAppUnitToFrame;
+  aRect.width = toDevPixels.width / devPixelsPerAppUnitToFrame;
+  aRect.height = toDevPixels.height / devPixelsPerAppUnitToFrame;
+  return TRANSFORM_SUCCEEDED;
+}
+
+nsRect
+nsLayoutUtils::GetRectRelativeToFrame(Element* aElement, nsIFrame* aFrame)
+{
+  if (!aElement || !aFrame) {
+    return nsRect();
+  }
+
+  nsIFrame* frame = aElement->GetPrimaryFrame();
+  if (!frame) {
+    return nsRect();
+  }
+
+  nsRect rect = frame->GetRectRelativeToSelf();
+  nsLayoutUtils::TransformResult rv =
+    nsLayoutUtils::TransformRect(frame, aFrame, rect);
+  if (rv != nsLayoutUtils::TRANSFORM_SUCCEEDED) {
+    return nsRect();
+  }
+
+  return rect;
+}
+
+bool
+nsLayoutUtils::ContainsPoint(const nsRect& aRect, const nsPoint& aPoint,
+                             nscoord aInflateSize)
+{
+  nsRect rect = aRect;
+  rect.Inflate(aInflateSize);
+  return rect.Contains(aPoint);
+}
+
+nsRect
+nsLayoutUtils::ClampRectToScrollFrames(nsIFrame* aFrame, const nsRect& aRect)
+{
+  nsIFrame* closestScrollFrame =
+    nsLayoutUtils::GetClosestFrameOfType(aFrame, nsGkAtoms::scrollFrame);
+
+  nsRect resultRect = aRect;
+
+  while (closestScrollFrame) {
+    nsIScrollableFrame* sf = do_QueryFrame(closestScrollFrame);
+
+    nsRect scrollPortRect = sf->GetScrollPortRect();
+    nsLayoutUtils::TransformRect(closestScrollFrame, aFrame, scrollPortRect);
+
+    resultRect = resultRect.Intersect(scrollPortRect);
+
+    // Check whether aRect is visible in the scroll frame or not.
+    if (resultRect.IsEmpty()) {
+      break;
+    }
+
+    // Get next ancestor scroll frame.
+    closestScrollFrame =
+      nsLayoutUtils::GetClosestFrameOfType(closestScrollFrame->GetParent(),
+                                           nsGkAtoms::scrollFrame);
+  }
+
+  return resultRect;
+}
+
+bool
+nsLayoutUtils::GetLayerTransformForFrame(nsIFrame* aFrame,
+                                         Matrix4x4* aTransform)
+{
+  // FIXME/bug 796690: we can sometimes compute a transform in these
+  // cases, it just increases complexity considerably.  Punt for now.
+  if (aFrame->Extend3DContext() || aFrame->HasTransformGetter()) {
+    return false;
+  }
+
+  nsIFrame* root = nsLayoutUtils::GetDisplayRootFrame(aFrame);
+  if (root->HasAnyStateBits(NS_FRAME_UPDATE_LAYER_TREE)) {
+    // Content may have been invalidated, so we can't reliably compute
+    // the "layer transform" in general.
+    return false;
+  }
+  // If the caller doesn't care about the value, early-return to skip
+  // overhead below.
+  if (!aTransform) {
+    return true;
+  }
+
+  nsDisplayListBuilder builder(root,
+                               nsDisplayListBuilderMode::TRANSFORM_COMPUTATION,
+                               false/*don't build caret*/);
+  nsDisplayList list;
+  nsDisplayTransform* item =
+    new (&builder) nsDisplayTransform(&builder, aFrame, &list, nsRect());
+
+  *aTransform = item->GetTransform();
+  item->~nsDisplayTransform();
+
+  return true;
+}
+
+static bool
+TransformGfxPointFromAncestor(nsIFrame *aFrame,
+                              const Point &aPoint,
+                              nsIFrame *aAncestor,
+                              Point* aOut)
+{
+  Matrix4x4 ctm = nsLayoutUtils::GetTransformToAncestor(aFrame, aAncestor);
+  ctm.Invert();
+  Point4D point = ctm.ProjectPoint(aPoint);
+  if (!point.HasPositiveWCoord()) {
+    return false;
+  }
+  *aOut = point.As2DPoint();
+  return true;
+}
+
+static Rect
+TransformGfxRectToAncestor(nsIFrame *aFrame,
+                           const Rect &aRect,
+                           const nsIFrame *aAncestor,
+                           bool* aPreservesAxisAlignedRectangles = nullptr,
+                           Maybe<Matrix4x4>* aMatrixCache = nullptr)
+{
+  Matrix4x4 ctm;
+  if (aMatrixCache && *aMatrixCache) {
+    // We are given a matrix to use, so use it
+    ctm = aMatrixCache->value();
+  } else {
+    // Else, compute it
+    ctm = nsLayoutUtils::GetTransformToAncestor(aFrame, aAncestor);
+    if (aMatrixCache) {
+      // and put it in the cache, if provided
+      *aMatrixCache = Some(ctm);
+    }
+  }
+  // Fill out the axis-alignment flag
+  if (aPreservesAxisAlignedRectangles) {
+    Matrix matrix2d;
+    *aPreservesAxisAlignedRectangles =
+      ctm.Is2D(&matrix2d) && matrix2d.PreservesAxisAlignedRectangles();
+  }
+  Rect maxBounds = Rect(-std::numeric_limits<float>::max() * 0.5,
+                        -std::numeric_limits<float>::max() * 0.5,
+                        std::numeric_limits<float>::max(),
+                        std::numeric_limits<float>::max());
+  return ctm.TransformAndClipBounds(aRect, maxBounds);
+}
+
+static SVGTextFrame*
+GetContainingSVGTextFrame(nsIFrame* aFrame)
+{
+  if (!aFrame->IsSVGText()) {
+    return nullptr;
+  }
+
+  return static_cast<SVGTextFrame*>
+    (nsLayoutUtils::GetClosestFrameOfType(aFrame->GetParent(),
+                                          nsGkAtoms::svgTextFrame));
+}
+
+nsPoint
+nsLayoutUtils::TransformAncestorPointToFrame(nsIFrame* aFrame,
+                                             const nsPoint& aPoint,
+                                             nsIFrame* aAncestor)
+{
+    SVGTextFrame* text = GetContainingSVGTextFrame(aFrame);
+
+    float factor = aFrame->PresContext()->AppUnitsPerDevPixel();
+    Point result(NSAppUnitsToFloatPixels(aPoint.x, factor),
+                 NSAppUnitsToFloatPixels(aPoint.y, factor));
+
+    if (text) {
+        if (!TransformGfxPointFromAncestor(text, result, aAncestor, &result)) {
+            return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+        }
+        result = text->TransformFramePointToTextChild(result, aFrame);
+    } else {
+        if (!TransformGfxPointFromAncestor(aFrame, result, nullptr, &result)) {
+            return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+        }
+    }
+
+    return nsPoint(NSFloatPixelsToAppUnits(float(result.x), factor),
+                   NSFloatPixelsToAppUnits(float(result.y), factor));
+}
+
+nsRect
+nsLayoutUtils::TransformFrameRectToAncestor(nsIFrame* aFrame,
+                                            const nsRect& aRect,
+                                            const nsIFrame* aAncestor,
+                                            bool* aPreservesAxisAlignedRectangles /* = nullptr */,
+                                            Maybe<Matrix4x4>* aMatrixCache /* = nullptr */)
+{
+  SVGTextFrame* text = GetContainingSVGTextFrame(aFrame);
+
+  float srcAppUnitsPerDevPixel = aFrame->PresContext()->AppUnitsPerDevPixel();
+  Rect result;
+
+  if (text) {
+    result = ToRect(text->TransformFrameRectFromTextChild(aRect, aFrame));
+    result = TransformGfxRectToAncestor(text, result, aAncestor, nullptr, aMatrixCache);
+    // TransformFrameRectFromTextChild could involve any kind of transform, we
+    // could drill down into it to get an answer out of it but we don't yet.
+    if (aPreservesAxisAlignedRectangles)
+      *aPreservesAxisAlignedRectangles = false;
+  } else {
+    result = Rect(NSAppUnitsToFloatPixels(aRect.x, srcAppUnitsPerDevPixel),
+                  NSAppUnitsToFloatPixels(aRect.y, srcAppUnitsPerDevPixel),
+                  NSAppUnitsToFloatPixels(aRect.width, srcAppUnitsPerDevPixel),
+                  NSAppUnitsToFloatPixels(aRect.height, srcAppUnitsPerDevPixel));
+    result = TransformGfxRectToAncestor(aFrame, result, aAncestor, aPreservesAxisAlignedRectangles, aMatrixCache);
+  }
+
+  float destAppUnitsPerDevPixel = aAncestor->PresContext()->AppUnitsPerDevPixel();
+  return nsRect(NSFloatPixelsToAppUnits(float(result.x), destAppUnitsPerDevPixel),
+                NSFloatPixelsToAppUnits(float(result.y), destAppUnitsPerDevPixel),
+                NSFloatPixelsToAppUnits(float(result.width), destAppUnitsPerDevPixel),
+                NSFloatPixelsToAppUnits(float(result.height), destAppUnitsPerDevPixel));
+}
+
+static LayoutDeviceIntPoint GetWidgetOffset(nsIWidget* aWidget, nsIWidget*& aRootWidget) {
+  LayoutDeviceIntPoint offset(0, 0);
+  while ((aWidget->WindowType() == eWindowType_child ||
+          aWidget->IsPlugin())) {
+    nsIWidget* parent = aWidget->GetParent();
+    if (!parent) {
+      break;
+    }
+    LayoutDeviceIntRect bounds = aWidget->GetBounds();
+    offset += bounds.TopLeft();
+    aWidget = parent;
+  }
+  aRootWidget = aWidget;
+  return offset;
+}
+
+static LayoutDeviceIntPoint
+WidgetToWidgetOffset(nsIWidget* aFrom, nsIWidget* aTo) {
+  nsIWidget* fromRoot;
+  LayoutDeviceIntPoint fromOffset = GetWidgetOffset(aFrom, fromRoot);
+  nsIWidget* toRoot;
+  LayoutDeviceIntPoint toOffset = GetWidgetOffset(aTo, toRoot);
+
+  if (fromRoot == toRoot) {
+    return fromOffset - toOffset;
+  }
+  return aFrom->WidgetToScreenOffset() - aTo->WidgetToScreenOffset();
+}
+
+nsPoint
+nsLayoutUtils::TranslateWidgetToView(nsPresContext* aPresContext,
+                                     nsIWidget* aWidget, const LayoutDeviceIntPoint& aPt,
+                                     nsView* aView)
+{
+  nsPoint viewOffset;
+  nsIWidget* viewWidget = aView->GetNearestWidget(&viewOffset);
+  if (!viewWidget) {
+    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  }
+
+  LayoutDeviceIntPoint widgetPoint = aPt + WidgetToWidgetOffset(aWidget, viewWidget);
+  nsPoint widgetAppUnits(aPresContext->DevPixelsToAppUnits(widgetPoint.x),
+                         aPresContext->DevPixelsToAppUnits(widgetPoint.y));
+  return widgetAppUnits - viewOffset;
+}
+
+LayoutDeviceIntPoint
+nsLayoutUtils::TranslateViewToWidget(nsPresContext* aPresContext,
+                                     nsView* aView, nsPoint aPt,
+                                     nsIWidget* aWidget)
+{
+  nsPoint viewOffset;
+  nsIWidget* viewWidget = aView->GetNearestWidget(&viewOffset);
+  if (!viewWidget) {
+    return LayoutDeviceIntPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
+  }
+
+  nsPoint pt = (aPt +
+  viewOffset).ApplyResolution(GetCurrentAPZResolutionScale(aPresContext->PresShell()));
+  LayoutDeviceIntPoint relativeToViewWidget(aPresContext->AppUnitsToDevPixels(pt.x),
+                                            aPresContext->AppUnitsToDevPixels(pt.y));
+  return relativeToViewWidget + WidgetToWidgetOffset(viewWidget, aWidget);
+}
+
+// Combine aNewBreakType with aOrigBreakType, but limit the break types
+// to StyleClear::Left, Right, Both.
+StyleClear
+nsLayoutUtils::CombineBreakType(StyleClear aOrigBreakType,
+                                StyleClear aNewBreakType)
+{
+  StyleClear breakType = aOrigBreakType;
+  switch(breakType) {
+    case StyleClear::Left:
+      if (StyleClear::Right == aNewBreakType ||
+          StyleClear::Both == aNewBreakType) {
+        breakType = StyleClear::Both;
+      }
+      break;
+    case StyleClear::Right:
+      if (StyleClear::Left == aNewBreakType ||
+          StyleClear::Both == aNewBreakType) {
+        breakType = StyleClear::Both;
+      }
+      break;
+    case StyleClear::None:
+      if (StyleClear::Left == aNewBreakType ||
+          StyleClear::Right == aNewBreakType ||
+          StyleClear::Both == aNewBreakType) {
+        breakType = aNewBreakType;
+      }
+      break;
+    default:
+      break;
+  }
+  return breakType;
+}
+
+#ifdef MOZ_DUMP_PAINTING
+#include <stdio.h>
+
+static bool gDumpEventList = false;
+
+// nsLayoutUtils::PaintFrame() can call itself recursively, so rather than
+// maintaining a single paint count, we need a stack.
+StaticAutoPtr<nsTArray<int>> gPaintCountStack;
+
+struct AutoNestedPaintCount {
+  AutoNestedPaintCount() {
+    gPaintCountStack->AppendElement(0);
+  }
+  ~AutoNestedPaintCount() {
+    gPaintCountStack->RemoveElementAt(gPaintCountStack->Length() - 1);
+  }
+};
+
+#endif
+
+nsIFrame*
+nsLayoutUtils::GetFrameForPoint(nsIFrame* aFrame, nsPoint aPt, uint32_t aFlags)
+{
+  PROFILER_LABEL("nsLayoutUtils", "GetFrameForPoint",
+    js::ProfileEntry::Category::GRAPHICS);
+
+  nsresult rv;
+  AutoTArray<nsIFrame*,8> outFrames;
+  rv = GetFramesForArea(aFrame, nsRect(aPt, nsSize(1, 1)), outFrames, aFlags);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+  return outFrames.Length() ? outFrames.ElementAt(0) : nullptr;
+}
+
+nsresult
+nsLayoutUtils::GetFramesForArea(nsIFrame* aFrame, const nsRect& aRect,
+                                nsTArray<nsIFrame*> &aOutFrames,
+                                uint32_t aFlags)
+{
+  PROFILER_LABEL("nsLayoutUtils", "GetFramesForArea",
+    js::ProfileEntry::Category::GRAPHICS);
+
+  nsDisplayListBuilder builder(aFrame,
+                               nsDisplayListBuilderMode::EVENT_DELIVERY,
+                               false);
+  nsDisplayList list;
+
+  if (aFlags & IGNORE_PAINT_SUPPRESSION) {
+    builder.IgnorePaintSuppression();
+  }
+
+  if (aFlags & IGNORE_ROOT_SCROLL_FRAME) {
+    nsIFrame* rootScrollFrame =
+      aFrame->PresContext()->PresShell()->GetRootScrollFrame();
+    if (rootScrollFrame) {
+      builder.SetIgnoreScrollFrame(rootScrollFrame);
+    }
+  }
+  if (aFlags & IGNORE_CROSS_DOC) {
+    builder.SetDescendIntoSubdocuments(false);
+  }
+
+  builder.EnterPresShell(aFrame);
+  aFrame->BuildDisplayListForStackingContext(&builder, aRect, &list);
+  builder.LeavePresShell(aFrame, nullptr);
+
+#ifdef MOZ_DUMP_PAINTING
+  if (gDumpEventList) {
+    fprintf_stderr(stderr, "Event handling --- (%d,%d):\n", aRect.x, aRect.y);
+
+    std::stringstream ss;
+    nsFrame::PrintDisplayList(&builder, list, ss);
+    print_stderr(ss);
+  }
+#endif
+
+  nsDisplayItem::HitTestState hitTestState;
+  list.HitTest(&builder, aRect, &hitTestState, &aOutFrames);
+  list.DeleteAll();
+  return NS_OK;
+}
+
+// aScrollFrameAsScrollable must be non-nullptr and queryable to an nsIFrame
+FrameMetrics
+nsLayoutUtils::CalculateBasicFrameMetrics(nsIScrollableFrame* aScrollFrame) {
+  nsIFrame* frame = do_QueryFrame(aScrollFrame);
+  MOZ_ASSERT(frame);
+
+  // Calculate the metrics necessary for calculating the displayport.
+  // This code has a lot in common with the code in ComputeFrameMetrics();
+  // we may want to refactor this at some point.
+  FrameMetrics metrics;
+  nsPresContext* presContext = frame->PresContext();
+  nsIPresShell* presShell = presContext->PresShell();
+  CSSToLayoutDeviceScale deviceScale = presContext->CSSToDevPixelScale();
+  float resolution = 1.0f;
+  if (frame == presShell->GetRootScrollFrame()) {
+    // Only the root scrollable frame for a given presShell should pick up
+    // the presShell's resolution. All the other frames are 1.0.
+    resolution = presShell->GetResolution();
+  }
+  // Note: unlike in ComputeFrameMetrics(), we don't know the full cumulative
+  // resolution including FrameMetrics::mExtraResolution, because layout hasn't
+  // chosen a resolution to paint at yet. However, the display port calculation
+  // divides out mExtraResolution anyways, so we get the correct result by
+  // setting the mCumulativeResolution to everything except the extra resolution
+  // and leaving mExtraResolution at 1.
+  LayoutDeviceToLayerScale2D cumulativeResolution(
+      presShell->GetCumulativeResolution()
+    * nsLayoutUtils::GetTransformToAncestorScale(frame));
+
+  LayerToParentLayerScale layerToParentLayerScale(1.0f);
+  metrics.SetDevPixelsPerCSSPixel(deviceScale);
+  metrics.SetPresShellResolution(resolution);
+  metrics.SetCumulativeResolution(cumulativeResolution);
+  metrics.SetZoom(deviceScale * cumulativeResolution * layerToParentLayerScale);
+
+  // Only the size of the composition bounds is relevant to the
+  // displayport calculation, not its origin.
+  nsSize compositionSize = nsLayoutUtils::CalculateCompositionSizeForFrame(frame);
+  LayoutDeviceToParentLayerScale2D compBoundsScale;
+  if (frame == presShell->GetRootScrollFrame() && presContext->IsRootContentDocument()) {
+    if (presContext->GetParentPresContext()) {
+      float res = presContext->GetParentPresContext()->PresShell()->GetCumulativeResolution();
+      compBoundsScale = LayoutDeviceToParentLayerScale2D(
+          LayoutDeviceToParentLayerScale(res));
+    }
+  } else {
+    compBoundsScale = cumulativeResolution * layerToParentLayerScale;
+  }
+  metrics.SetCompositionBounds(
+      LayoutDeviceRect::FromAppUnits(nsRect(nsPoint(0, 0), compositionSize),
+                                       presContext->AppUnitsPerDevPixel())
+      * compBoundsScale);
+
+  metrics.SetRootCompositionSize(
+      nsLayoutUtils::CalculateRootCompositionSize(frame, false, metrics));
+
+  metrics.SetScrollOffset(CSSPoint::FromAppUnits(
+      aScrollFrame->GetScrollPosition()));
+
+  metrics.SetScrollableRect(CSSRect::FromAppUnits(
+      nsLayoutUtils::CalculateScrollableRectForFrame(aScrollFrame, nullptr)));
+
+  return metrics;
+}
+
+bool
+nsLayoutUtils::CalculateAndSetDisplayPortMargins(nsIScrollableFrame* aScrollFrame,
+                                                 RepaintMode aRepaintMode) {
+  nsIFrame* frame = do_QueryFrame(aScrollFrame);
+  MOZ_ASSERT(frame);
+  nsIContent* content = frame->GetContent();
+  MOZ_ASSERT(content);
+
+  FrameMetrics metrics = CalculateBasicFrameMetrics(aScrollFrame);
+  ScreenMargin displayportMargins = APZCTreeManager::CalculatePendingDisplayPort(
+      metrics, ParentLayerPoint(0.0f, 0.0f));
+  nsIPresShell* presShell = frame->PresContext()->GetPresShell();
+  return nsLayoutUtils::SetDisplayPortMargins(
+      content, presShell, displayportMargins, 0, aRepaintMode);
+}
+
+void
+nsLayoutUtils::MaybeCreateDisplayPort(nsDisplayListBuilder& aBuilder,
+                                      nsIFrame* aScrollFrame) {
+  nsIContent* content = aScrollFrame->GetContent();
+  nsIScrollableFrame* scrollableFrame = do_QueryFrame(aScrollFrame);
+  if (!content || !scrollableFrame) {
+    return;
+  }
+
+  bool haveDisplayPort = HasDisplayPort(content);
+
+  // We perform an optimization where we ensure that at least one
+  // async-scrollable frame (i.e. one that WantsAsyncScroll()) has a displayport.
+  // If that's not the case yet, and we are async-scrollable, we will get a
+  // displayport.
+  if (aBuilder.IsPaintingToWindow() &&
+      nsLayoutUtils::AsyncPanZoomEnabled(aScrollFrame) &&
+      !aBuilder.HaveScrollableDisplayPort() &&
+      scrollableFrame->WantAsyncScroll()) {
+
+    // If we don't already have a displayport, calculate and set one.
+    if (!haveDisplayPort) {
+      CalculateAndSetDisplayPortMargins(scrollableFrame, nsLayoutUtils::RepaintMode::DoNotRepaint);
+#ifdef DEBUG
+      haveDisplayPort = HasDisplayPort(content);
+      MOZ_ASSERT(haveDisplayPort, "should have a displayport after having just set it");
+#endif
+    }
+
+    // Record that the we now have a scrollable display port.
+    aBuilder.SetHaveScrollableDisplayPort();
+  }
+}
+
+nsIScrollableFrame*
+nsLayoutUtils::GetAsyncScrollableAncestorFrame(nsIFrame* aTarget)
+{
+  uint32_t flags = nsLayoutUtils::SCROLLABLE_ALWAYS_MATCH_ROOT
+                 | nsLayoutUtils::SCROLLABLE_ONLY_ASYNC_SCROLLABLE
+                 | nsLayoutUtils::SCROLLABLE_FIXEDPOS_FINDS_ROOT;
+  return nsLayoutUtils::GetNearestScrollableFrame(aTarget, flags);
+}
+
+void
+nsLayoutUtils::SetZeroMarginDisplayPortOnAsyncScrollableAncestors(nsIFrame* aFrame,
+                                                                  RepaintMode aRepaintMode)
+{
+  nsIFrame* frame = aFrame;
+  while (frame) {
+    frame = nsLayoutUtils::GetCrossDocParentFrame(frame);
+    if (!frame) {
+      break;
+    }
+    nsIScrollableFrame* scrollAncestor = GetAsyncScrollableAncestorFrame(frame);
+    if (!scrollAncestor) {
+      break;
+    }
+    frame = do_QueryFrame(scrollAncestor);
+    MOZ_ASSERT(frame);
+    MOZ_ASSERT(scrollAncestor->WantAsyncScroll() ||
+      frame->PresContext()->PresShell()->GetRootScrollFrame() == frame);
+    if (nsLayoutUtils::AsyncPanZoomEnabled(frame) &&
+        !nsLayoutUtils::HasDisplayPort(frame->GetContent())) {
+      nsLayoutUtils::SetDisplayPortMargins(
+        frame->GetContent(), frame->PresContext()->PresShell(), ScreenMargin(), 0,
+        aRepaintMode);
+    }
+  }
+}
+
+void
+nsLayoutUtils::ExpireDisplayPortOnAsyncScrollableAncestor(nsIFrame* aFrame)
+{
+  nsIFrame* frame = aFrame;
+  while (frame) {
+    frame = nsLayoutUtils::GetCrossDocParentFrame(frame);
+    if (!frame) {
+      break;
+    }
+    nsIScrollableFrame* scrollAncestor = GetAsyncScrollableAncestorFrame(frame);
+    if (!scrollAncestor) {
+      break;
+    }
+    frame = do_QueryFrame(scrollAncestor);
+    MOZ_ASSERT(frame);
+    if (!frame) {
+      break;
+    }
+    MOZ_ASSERT(scrollAncestor->WantAsyncScroll() ||
+      frame->PresContext()->PresShell()->GetRootScrollFrame() == frame);
+    if (nsLayoutUtils::HasDisplayPort(frame->GetContent())) {
+      scrollAncestor->TriggerDisplayPortExpiration();
+      // Stop after the first trigger. If it failed, there's no point in
+      // continuing because all the rest of the frames we encounter are going
+      // to be ancestors of |scrollAncestor| which will keep its displayport.
+      // If the trigger succeeded, we stop because when the trigger executes
+      // it will call this function again to trigger the next ancestor up the
+      // chain.
+      break;
+    }
+  }
+}
+
+nsresult
+nsLayoutUtils::PaintFrame(nsRenderingContext* aRenderingContext, nsIFrame* aFrame,
+                          const nsRegion& aDirtyRegion, nscolor aBackstop,
+                          nsDisplayListBuilderMode aBuilderMode,
+                          PaintFrameFlags aFlags)
+{
+  PROFILER_LABEL("nsLayoutUtils", "PaintFrame",
+    js::ProfileEntry::Category::GRAPHICS);
+
+#ifdef MOZ_DUMP_PAINTING
+  if (!gPaintCountStack) {
+    gPaintCountStack = new nsTArray<int>();
+    ClearOnShutdown(&gPaintCountStack);
+
+    gPaintCountStack->AppendElement(0);
+  }
+  ++gPaintCountStack->LastElement();
+  AutoNestedPaintCount nestedPaintCount;
+#endif
+
+  if (aFlags & PaintFrameFlags::PAINT_WIDGET_LAYERS) {
+    nsView* view = aFrame->GetView();
+    if (!(view && view->GetWidget() && GetDisplayRootFrame(aFrame) == aFrame)) {
+      aFlags &= ~PaintFrameFlags::PAINT_WIDGET_LAYERS;
+      NS_ASSERTION(aRenderingContext, "need a rendering context");
+    }
+  }
+
+  nsPresContext* presContext = aFrame->PresContext();
+  nsIPresShell* presShell = presContext->PresShell();
+  nsRootPresContext* rootPresContext = presContext->GetRootPresContext();
+  if (!rootPresContext) {
+    return NS_OK;
+  }
+
+  TimeStamp startBuildDisplayList = TimeStamp::Now();
+  nsDisplayListBuilder builder(aFrame, aBuilderMode,
+                               !(aFlags & PaintFrameFlags::PAINT_HIDE_CARET));
+  if (aFlags & PaintFrameFlags::PAINT_IN_TRANSFORM) {
+    builder.SetInTransform(true);
+  }
+  if (aFlags & PaintFrameFlags::PAINT_SYNC_DECODE_IMAGES) {
+    builder.SetSyncDecodeImages(true);
+  }
+  if (aFlags & (PaintFrameFlags::PAINT_WIDGET_LAYERS |
+                PaintFrameFlags::PAINT_TO_WINDOW)) {
+    builder.SetPaintingToWindow(true);
+  }
+  if (aFlags & PaintFrameFlags::PAINT_IGNORE_SUPPRESSION) {
+    builder.IgnorePaintSuppression();
+  }
+
+  nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();
+  if (rootScrollFrame && !aFrame->GetParent()) {
+    nsIScrollableFrame* rootScrollableFrame = presShell->GetRootScrollFrameAsScrollable();
+    MOZ_ASSERT(rootScrollableFrame);
+    nsRect displayPortBase = aFrame->GetVisualOverflowRectRelativeToSelf();
+    Unused << rootScrollableFrame->DecideScrollableLayer(&builder, &displayPortBase,
+                /* aAllowCreateDisplayPort = */ true);
+  }
+
+  nsRegion visibleRegion;
+  if (aFlags & PaintFrameFlags::PAINT_WIDGET_LAYERS) {
+    // This layer tree will be reused, so we'll need to calculate it
+    // for the whole "visible" area of the window
+    //
+    // |ignoreViewportScrolling| and |usingDisplayPort| are persistent
+    // document-rendering state.  We rely on PresShell to flush
+    // retained layers as needed when that persistent state changes.
+    visibleRegion = aFrame->GetVisualOverflowRectRelativeToSelf();
+  } else {
+    visibleRegion = aDirtyRegion;
+  }
+
+  nsDisplayList list;
+
+  // If the root has embedded plugins, flag the builder so we know we'll need
+  // to update plugin geometry after painting.
+  if ((aFlags & PaintFrameFlags::PAINT_WIDGET_LAYERS) &&
+      !(aFlags & PaintFrameFlags::PAINT_DOCUMENT_RELATIVE) &&
+      rootPresContext->NeedToComputePluginGeometryUpdates()) {
+    builder.SetWillComputePluginGeometry(true);
+  }
+
+  nsRect canvasArea(nsPoint(0, 0), aFrame->GetSize());
+  bool ignoreViewportScrolling =
+    aFrame->GetParent() ? false : presShell->IgnoringViewportScrolling();
+  if (ignoreViewportScrolling && rootScrollFrame) {
+    nsIScrollableFrame* rootScrollableFrame =
+      presShell->GetRootScrollFrameAsScrollable();
+    if (aFlags & PaintFrameFlags::PAINT_DOCUMENT_RELATIVE) {
+      // Make visibleRegion and aRenderingContext relative to the
+      // scrolled frame instead of the root frame.
+      nsPoint pos = rootScrollableFrame->GetScrollPosition();
+      visibleRegion.MoveBy(-pos);
+      if (aRenderingContext) {
+        gfxPoint devPixelOffset =
+          nsLayoutUtils::PointToGfxPoint(pos,
+                                         presContext->AppUnitsPerDevPixel());
+        aRenderingContext->ThebesContext()->SetMatrix(
+          aRenderingContext->ThebesContext()->CurrentMatrix().Translate(devPixelOffset));
+      }
+    }
+    builder.SetIgnoreScrollFrame(rootScrollFrame);
+
+    nsCanvasFrame* canvasFrame =
+      do_QueryFrame(rootScrollableFrame->GetScrolledFrame());
+    if (canvasFrame) {
+      // Use UnionRect here to ensure that areas where the scrollbars
+      // were are still filled with the background color.
+      canvasArea.UnionRect(canvasArea,
+        canvasFrame->CanvasArea() + builder.ToReferenceFrame(canvasFrame));
+    }
+  }
+
+  builder.EnterPresShell(aFrame);
+  nsRect dirtyRect = visibleRegion.GetBounds();
+  {
+    // If a scrollable container layer is created in nsDisplayList::PaintForFrame,
+    // it will be the scroll parent for display items that are built in the
+    // BuildDisplayListForStackingContext call below. We need to set the scroll
+    // parent on the display list builder while we build those items, so that they
+    // can pick up their scroll parent's id.
+    ViewID id = FrameMetrics::NULL_SCROLL_ID;
+    if (ignoreViewportScrolling && presContext->IsRootContentDocument()) {
+      if (nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame()) {
+        if (nsIContent* content = rootScrollFrame->GetContent()) {
+          id = nsLayoutUtils::FindOrCreateIDFor(content);
+        }
+      }
+    }
+    else if (presShell->GetDocument() && presShell->GetDocument()->IsRootDisplayDocument()
+        && !presShell->GetRootScrollFrame()) {
+      // In cases where the root document is a XUL document, we want to take
+      // the ViewID from the root element, as that will be the ViewID of the
+      // root APZC in the tree. Skip doing this in cases where we know
+      // nsGfxScrollFrame::BuilDisplayList will do it instead.
+      if (dom::Element* element = presShell->GetDocument()->GetDocumentElement()) {
+        id = nsLayoutUtils::FindOrCreateIDFor(element);
+      }
+    }
+
+    nsDisplayListBuilder::AutoCurrentScrollParentIdSetter idSetter(&builder, id);
+
+    PROFILER_LABEL("nsLayoutUtils", "PaintFrame::BuildDisplayList",
+      js::ProfileEntry::Category::GRAPHICS);
+
+
+    PaintTelemetry::AutoRecord record(PaintTelemetry::Metric::DisplayList);
+    aFrame->BuildDisplayListForStackingContext(&builder, dirtyRect, &list);
+  }
+
+  nsIAtom* frameType = aFrame->GetType();
+
+  // For the viewport frame in print preview/page layout we want to paint
+  // the grey background behind the page, not the canvas color.
+  if (frameType == nsGkAtoms::viewportFrame &&
+      nsLayoutUtils::NeedsPrintPreviewBackground(presContext)) {
+    nsRect bounds = nsRect(builder.ToReferenceFrame(aFrame),
+                           aFrame->GetSize());
+    nsDisplayListBuilder::AutoBuildingDisplayList
+      buildingDisplayList(&builder, aFrame, bounds, false);
+    presShell->AddPrintPreviewBackgroundItem(builder, list, aFrame, bounds);
+  } else if (frameType != nsGkAtoms::pageFrame) {
+    // For printing, this function is first called on an nsPageFrame, which
+    // creates a display list with a PageContent item. The PageContent item's
+    // paint function calls this function on the nsPageFrame's child which is
+    // an nsPageContentFrame. We only want to add the canvas background color
+    // item once, for the nsPageContentFrame.
+
+    // Add the canvas background color to the bottom of the list. This
+    // happens after we've built the list so that AddCanvasBackgroundColorItem
+    // can monkey with the contents if necessary.
+    canvasArea.IntersectRect(canvasArea, visibleRegion.GetBounds());
+    nsDisplayListBuilder::AutoBuildingDisplayList
+      buildingDisplayList(&builder, aFrame, canvasArea, false);
+    presShell->AddCanvasBackgroundColorItem(
+           builder, list, aFrame, canvasArea, aBackstop);
+  }
+
+  builder.LeavePresShell(aFrame, &list);
+  Telemetry::AccumulateTimeDelta(Telemetry::PAINT_BUILD_DISPLAYLIST_TIME,
+                                 startBuildDisplayList);
+
+  bool profilerNeedsDisplayList = profiler_feature_active("displaylistdump");
+  bool consoleNeedsDisplayList = gfxUtils::DumpDisplayList() || gfxEnv::DumpPaint();
+#ifdef MOZ_DUMP_PAINTING
+  FILE* savedDumpFile = gfxUtils::sDumpPaintFile;
+#endif
+
+  UniquePtr<std::stringstream> ss;
+  if (consoleNeedsDisplayList || profilerNeedsDisplayList) {
+    ss = MakeUnique<std::stringstream>();
+#ifdef MOZ_DUMP_PAINTING
+    if (gfxEnv::DumpPaintToFile()) {
+      nsCString string("dump-");
+      // Include the process ID in the dump file name, to make sure that in an
+      // e10s setup different processes don't clobber each other's dump files.
+      string.AppendInt(getpid());
+      for (int paintCount : *gPaintCountStack) {
+        string.AppendLiteral("-");
+        string.AppendInt(paintCount);
+      }
+      string.AppendLiteral(".html");
+      gfxUtils::sDumpPaintFile = fopen(string.BeginReading(), "w");
+    } else {
+      gfxUtils::sDumpPaintFile = stderr;
+    }
+    if (gfxEnv::DumpPaintToFile()) {
+      *ss << "<html><head><script>\n"
+             "var array = {};\n"
+             "function ViewImage(index) { \n"
+             "  var image = document.getElementById(index);\n"
+             "  if (image.src) {\n"
+             "    image.removeAttribute('src');\n"
+             "  } else {\n"
+             "    image.src = array[index];\n"
+             "  }\n"
+             "}</script></head><body>";
+    }
+#endif
+    *ss << nsPrintfCString("Painting --- before optimization (dirty %d,%d,%d,%d):\n",
+            dirtyRect.x, dirtyRect.y, dirtyRect.width, dirtyRect.height).get();
+    nsFrame::PrintDisplayList(&builder, list, *ss, gfxEnv::DumpPaintToFile());
+
+    if (gfxEnv::DumpPaint() || gfxEnv::DumpPaintItems()) {
+      // Flush stream now to avoid reordering dump output relative to
+      // messages dumped by PaintRoot below.
+      if (profilerNeedsDisplayList && !consoleNeedsDisplayList) {
+        profiler_log(ss->str().c_str());
+      } else {
+        // Send to the console which will send to the profiler if required.
+        fprint_stderr(gfxUtils::sDumpPaintFile, *ss);
+      }
+      ss = MakeUnique<std::stringstream>();
+    }
+  }
+
+  uint32_t flags = nsDisplayList::PAINT_DEFAULT;
+  if (aFlags & PaintFrameFlags::PAINT_WIDGET_LAYERS) {
+    flags |= nsDisplayList::PAINT_USE_WIDGET_LAYERS;
+    if (!(aFlags & PaintFrameFlags::PAINT_DOCUMENT_RELATIVE)) {
+      nsIWidget *widget = aFrame->GetNearestWidget();
+      if (widget) {
+        // If we're finished building display list items for painting of the outermost
+        // pres shell, notify the widget about any toolbars we've encountered.
+        widget->UpdateThemeGeometries(builder.GetThemeGeometries());
+      }
+    }
+  }
+  if (aFlags & PaintFrameFlags::PAINT_EXISTING_TRANSACTION) {
+    flags |= nsDisplayList::PAINT_EXISTING_TRANSACTION;
+  }
+  if (aFlags & PaintFrameFlags::PAINT_NO_COMPOSITE) {
+    flags |= nsDisplayList::PAINT_NO_COMPOSITE;
+  }
+  if (aFlags & PaintFrameFlags::PAINT_COMPRESSED) {
+    flags |= nsDisplayList::PAINT_COMPRESSED;
+  }
+
+  TimeStamp paintStart = TimeStamp::Now();
+  RefPtr<LayerManager> layerManager
+    = list.PaintRoot(&builder, aRenderingContext, flags);
+  Telemetry::AccumulateTimeDelta(Telemetry::PAINT_RASTERIZE_TIME,
+                                 paintStart);
+
+  if (gfxPrefs::GfxLoggingPaintedPixelCountEnabled()) {
+    TimeStamp now = TimeStamp::Now();
+    float rasterizeTime = (now - paintStart).ToMilliseconds();
+    uint32_t pixelCount = layerManager->GetAndClearPaintedPixelCount();
+    static std::vector<std::pair<TimeStamp, uint32_t>> history;
+    if (pixelCount) {
+      history.push_back(std::make_pair(now, pixelCount));
+    }
+    uint32_t paintedInLastSecond = 0;
+    for (auto i = history.begin(); i != history.end(); i++) {
+      if ((now - i->first).ToMilliseconds() > 1000.0f) {
+        // more than 1000ms ago, don't count it
+        continue;
+      }
+      if (paintedInLastSecond == 0) {
+        // This is the first one in the last 1000ms, so drop everything earlier
+        history.erase(history.begin(), i);
+        i = history.begin();
+      }
+      paintedInLastSecond += i->second;
+      MOZ_ASSERT(paintedInLastSecond); // all historical pixel counts are > 0
+    }
+    printf_stderr("Painted %u pixels in %fms (%u in the last 1000ms)\n",
+        pixelCount, rasterizeTime, paintedInLastSecond);
+  }
+
+  if (consoleNeedsDisplayList || profilerNeedsDisplayList) {
+    *ss << "Painting --- after optimization:\n";
+    nsFrame::PrintDisplayList(&builder, list, *ss, gfxEnv::DumpPaintToFile());
+
+    *ss << "Painting --- layer tree:\n";
+    if (layerManager) {
+      FrameLayerBuilder::DumpRetainedLayerTree(layerManager, *ss,
+                                               gfxEnv::DumpPaintToFile());
+    }
+
+    if (profilerNeedsDisplayList && !consoleNeedsDisplayList) {
+      profiler_log(ss->str().c_str());
+    } else {
+      // Send to the console which will send to the profiler if required.
+      fprint_stderr(gfxUtils::sDumpPaintFile, *ss);
+    }
+
+#ifdef MOZ_DUMP_PAINTING
+    if (gfxEnv::DumpPaintToFile()) {
+      *ss << "</body></html>";
+    }
+    if (gfxEnv::DumpPaintToFile()) {
+      fclose(gfxUtils::sDumpPaintFile);
+    }
+    gfxUtils::sDumpPaintFile = savedDumpFile;
+#endif
+
+    std::stringstream lsStream;
+    nsFrame::PrintDisplayList(&builder, list, lsStream);
+    layerManager->GetRoot()->SetDisplayListLog(lsStream.str().c_str());
+  }
+
+#ifdef MOZ_DUMP_PAINTING
+  if (gfxPrefs::DumpClientLayers()) {
+    std::stringstream ss;
+    FrameLayerBuilder::DumpRetainedLayerTree(layerManager, ss, false);
+    print_stderr(ss);
+  }
+#endif
+
+  // Update the widget's opaque region information. This sets
+  // glass boundaries on Windows. Also set up the window dragging region
+  // and plugin clip regions and bounds.
+  if ((aFlags & PaintFrameFlags::PAINT_WIDGET_LAYERS) &&
+      !(aFlags & PaintFrameFlags::PAINT_DOCUMENT_RELATIVE)) {
+    nsIWidget *widget = aFrame->GetNearestWidget();
+    if (widget) {
+      nsRegion opaqueRegion;
+      opaqueRegion.And(builder.GetWindowExcludeGlassRegion(), builder.GetWindowOpaqueRegion());
+      widget->UpdateOpaqueRegion(
+        LayoutDeviceIntRegion::FromUnknownRegion(
+          opaqueRegion.ToNearestPixels(presContext->AppUnitsPerDevPixel())));
+
+      widget->UpdateWindowDraggingRegion(builder.GetWindowDraggingRegion());
+    }
+  }
+
+  if (builder.WillComputePluginGeometry()) {
+    // For single process compute and apply plugin geometry updates to plugin
+    // windows, then request composition. For content processes skip eveything
+    // except requesting composition. Geometry updates were calculated and
+    // shipped to the chrome process in nsDisplayList when the layer
+    // transaction completed.
+    if (XRE_IsParentProcess()) {
+      rootPresContext->ComputePluginGeometryUpdates(aFrame, &builder, &list);
+      // We're not going to get a WillPaintWindow event here if we didn't do
+      // widget invalidation, so just apply the plugin geometry update here
+      // instead. We could instead have the compositor send back an equivalent
+      // to WillPaintWindow, but it should be close enough to now not to matter.
+      if (layerManager && !layerManager->NeedsWidgetInvalidation()) {
+        rootPresContext->ApplyPluginGeometryUpdates();
+      }
+    }
+
+    // We told the compositor thread not to composite when it received the
+    // transaction because we wanted to update plugins first. Schedule the
+    // composite now.
+    if (layerManager) {
+      layerManager->Composite();
+    }
+  }
+
+
+  // Flush the list so we don't trigger the IsEmpty-on-destruction assertion
+  list.DeleteAll();
+  return NS_OK;
+}
+
+/**
+ * Uses a binary search for find where the cursor falls in the line of text
+ * It also keeps track of the part of the string that has already been measured
+ * so it doesn't have to keep measuring the same text over and over
+ *
+ * @param "aBaseWidth" contains the width in twips of the portion
+ * of the text that has already been measured, and aBaseInx contains
+ * the index of the text that has already been measured.
+ *
+ * @param aTextWidth returns the (in twips) the length of the text that falls
+ * before the cursor aIndex contains the index of the text where the cursor falls
+ */
+bool
+nsLayoutUtils::BinarySearchForPosition(DrawTarget* aDrawTarget,
+                                       nsFontMetrics& aFontMetrics,
+                        const char16_t* aText,
+                        int32_t    aBaseWidth,
+                        int32_t    aBaseInx,
+                        int32_t    aStartInx,
+                        int32_t    aEndInx,
+                        int32_t    aCursorPos,
+                        int32_t&   aIndex,
+                        int32_t&   aTextWidth)
+{
+  int32_t range = aEndInx - aStartInx;
+  if ((range == 1) || (range == 2 && NS_IS_HIGH_SURROGATE(aText[aStartInx]))) {
+    aIndex   = aStartInx + aBaseInx;
+    aTextWidth = nsLayoutUtils::AppUnitWidthOfString(aText, aIndex,
+                                                     aFontMetrics, aDrawTarget);
+    return true;
+  }
+
+  int32_t inx = aStartInx + (range / 2);
+
+  // Make sure we don't leave a dangling low surrogate
+  if (NS_IS_HIGH_SURROGATE(aText[inx-1]))
+    inx++;
+
+  int32_t textWidth = nsLayoutUtils::AppUnitWidthOfString(aText, inx,
+                                                          aFontMetrics,
+                                                          aDrawTarget);
+
+  int32_t fullWidth = aBaseWidth + textWidth;
+  if (fullWidth == aCursorPos) {
+    aTextWidth = textWidth;
+    aIndex = inx;
+    return true;
+  } else if (aCursorPos < fullWidth) {
+    aTextWidth = aBaseWidth;
+    if (BinarySearchForPosition(aDrawTarget, aFontMetrics, aText, aBaseWidth,
+                                aBaseInx, aStartInx, inx, aCursorPos, aIndex,
+                                aTextWidth)) {
+      return true;
+    }
+  } else {
+    aTextWidth = fullWidth;
+    if (BinarySearchForPosition(aDrawTarget, aFontMetrics, aText, aBaseWidth,
+                                aBaseInx, inx, aEndInx, aCursorPos, aIndex,
+                                aTextWidth)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+static void
+AddBoxesForFrame(nsIFrame* aFrame,
+                 nsLayoutUtils::BoxCallback* aCallback)
+{
+  nsIAtom* pseudoType = aFrame->StyleContext()->GetPseudo();
+
+  if (pseudoType == nsCSSAnonBoxes::tableWrapper) {
+    AddBoxesForFrame(aFrame->PrincipalChildList().FirstChild(), aCallback);
+    if (aCallback->mIncludeCaptionBoxForTable) {
+      nsIFrame* kid = aFrame->GetChildList(nsIFrame::kCaptionList).FirstChild();
+      if (kid) {
+        AddBoxesForFrame(kid, aCallback);
+      }
+    }
+  } else if (pseudoType == nsCSSAnonBoxes::mozAnonymousBlock ||
+             pseudoType == nsCSSAnonBoxes::mozAnonymousPositionedBlock ||
+             pseudoType == nsCSSAnonBoxes::mozMathMLAnonymousBlock ||
+             pseudoType == nsCSSAnonBoxes::mozXULAnonymousBlock) {
+    for (nsIFrame* kid : aFrame->PrincipalChildList()) {
+      AddBoxesForFrame(kid, aCallback);
+    }
+  } else {
+    aCallback->AddBox(aFrame);
+  }
+}
+
+void
+nsLayoutUtils::GetAllInFlowBoxes(nsIFrame* aFrame, BoxCallback* aCallback)
+{
+  while (aFrame) {
+    AddBoxesForFrame(aFrame, aCallback);
+    aFrame = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(aFrame);
+  }
+}
+
+nsIFrame*
+nsLayoutUtils::GetFirstNonAnonymousFrame(nsIFrame* aFrame)
+{
+  while (aFrame) {
+    nsIAtom* pseudoType = aFrame->StyleContext()->GetPseudo();
+
+    if (pseudoType == nsCSSAnonBoxes::tableWrapper) {
+      nsIFrame* f = GetFirstNonAnonymousFrame(aFrame->PrincipalChildList().FirstChild());
+      if (f) {
+        return f;
+      }
+      nsIFrame* kid = aFrame->GetChildList(nsIFrame::kCaptionList).FirstChild();
+      if (kid) {
+        f = GetFirstNonAnonymousFrame(kid);
+        if (f) {
+          return f;
+        }
+      }
+    } else if (pseudoType == nsCSSAnonBoxes::mozAnonymousBlock ||
+               pseudoType == nsCSSAnonBoxes::mozAnonymousPositionedBlock ||
+               pseudoType == nsCSSAnonBoxes::mozMathMLAnonymousBlock ||
+               pseudoType == nsCSSAnonBoxes::mozXULAnonymousBlock) {
+      for (nsIFrame* kid : aFrame->PrincipalChildList()) {
+        nsIFrame* f = GetFirstNonAnonymousFrame(kid);
+        if (f) {
+          return f;
+        }
+      }
+    } else {
+      return aFrame;
+    }
+
+    aFrame = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(aFrame);
+  }
+  return nullptr;
+}
+
+struct BoxToRect : public nsLayoutUtils::BoxCallback {
+  nsIFrame* mRelativeTo;
+  nsLayoutUtils::RectCallback* mCallback;
+  uint32_t mFlags;
+
+  BoxToRect(nsIFrame* aRelativeTo, nsLayoutUtils::RectCallback* aCallback,
+            uint32_t aFlags)
+    : mRelativeTo(aRelativeTo), mCallback(aCallback), mFlags(aFlags) {}
+
+  virtual void AddBox(nsIFrame* aFrame) override {
+    nsRect r;
+    nsIFrame* outer = nsSVGUtils::GetOuterSVGFrameAndCoveredRegion(aFrame, &r);
+    if (!outer) {
+      outer = aFrame;
+      switch (mFlags & nsLayoutUtils::RECTS_WHICH_BOX_MASK) {
+        case nsLayoutUtils::RECTS_USE_CONTENT_BOX:
+          r = aFrame->GetContentRectRelativeToSelf();
+          break;
+        case nsLayoutUtils::RECTS_USE_PADDING_BOX:
+          r = aFrame->GetPaddingRectRelativeToSelf();
+          break;
+        case nsLayoutUtils::RECTS_USE_MARGIN_BOX:
+          r = aFrame->GetMarginRectRelativeToSelf();
+          break;
+        default: // Use the border box
+          r = aFrame->GetRectRelativeToSelf();
+      }
+    }
+    if (mFlags & nsLayoutUtils::RECTS_ACCOUNT_FOR_TRANSFORMS) {
+      r = nsLayoutUtils::TransformFrameRectToAncestor(outer, r, mRelativeTo);
+    } else {
+      r += outer->GetOffsetTo(mRelativeTo);
+    }
+    mCallback->AddRect(r);
+  }
+};
+
+struct BoxToRectAndText : public BoxToRect {
+  mozilla::dom::DOMStringList* mTextList;
+
+  BoxToRectAndText(nsIFrame* aRelativeTo, nsLayoutUtils::RectCallback* aCallback,
+                   mozilla::dom::DOMStringList* aTextList, uint32_t aFlags)
+    : BoxToRect(aRelativeTo, aCallback, aFlags), mTextList(aTextList) {}
+
+  virtual void AddBox(nsIFrame* aFrame) override {
+    BoxToRect::AddBox(aFrame);
+    if (mTextList) {
+      nsIContent* content = aFrame->GetContent();
+      nsAutoString textContent;
+      mozilla::ErrorResult err; // ignored
+      content->GetTextContent(textContent, err);
+      mTextList->Add(textContent);
+    }
+  }
+};
+
+void
+nsLayoutUtils::GetAllInFlowRects(nsIFrame* aFrame, nsIFrame* aRelativeTo,
+                                 RectCallback* aCallback, uint32_t aFlags)
+{
+  BoxToRect converter(aRelativeTo, aCallback, aFlags);
+  GetAllInFlowBoxes(aFrame, &converter);
+}
+
+void
+nsLayoutUtils::GetAllInFlowRectsAndTexts(nsIFrame* aFrame, nsIFrame* aRelativeTo,
+                                         RectCallback* aCallback,
+                                         mozilla::dom::DOMStringList* aTextList,
+                                         uint32_t aFlags)
+{
+  BoxToRectAndText converter(aRelativeTo, aCallback, aTextList, aFlags);
+  GetAllInFlowBoxes(aFrame, &converter);
+}
+
+nsLayoutUtils::RectAccumulator::RectAccumulator() : mSeenFirstRect(false) {}
+
+void nsLayoutUtils::RectAccumulator::AddRect(const nsRect& aRect) {
+  mResultRect.UnionRect(mResultRect, aRect);
+  if (!mSeenFirstRect) {
+    mSeenFirstRect = true;
+    mFirstRect = aRect;
+  }
+}
+
+nsLayoutUtils::RectListBuilder::RectListBuilder(DOMRectList* aList)
+  : mRectList(aList)
+{
+}
+
+void nsLayoutUtils::RectListBuilder::AddRect(const nsRect& aRect) {
+  RefPtr<DOMRect> rect = new DOMRect(mRectList);
+
+  rect->SetLayoutRect(aRect);
+  mRectList->Append(rect);
+}
+
+nsIFrame* nsLayoutUtils::GetContainingBlockForClientRect(nsIFrame* aFrame)
+{
+  return aFrame->PresContext()->PresShell()->GetRootFrame();
+}
+
+nsRect
+nsLayoutUtils::GetAllInFlowRectsUnion(nsIFrame* aFrame, nsIFrame* aRelativeTo,
+                                      uint32_t aFlags) {
+  RectAccumulator accumulator;
+  GetAllInFlowRects(aFrame, aRelativeTo, &accumulator, aFlags);
+  return accumulator.mResultRect.IsEmpty() ? accumulator.mFirstRect
+          : accumulator.mResultRect;
+}
+
+nsRect
+nsLayoutUtils::GetTextShadowRectsUnion(const nsRect& aTextAndDecorationsRect,
+                                       nsIFrame* aFrame,
+                                       uint32_t aFlags)
+{
+  const nsStyleText* textStyle = aFrame->StyleText();
+  if (!textStyle->HasTextShadow())
+    return aTextAndDecorationsRect;
+
+  nsRect resultRect = aTextAndDecorationsRect;
+  int32_t A2D = aFrame->PresContext()->AppUnitsPerDevPixel();
+  for (uint32_t i = 0; i < textStyle->mTextShadow->Length(); ++i) {
+    nsCSSShadowItem* shadow = textStyle->mTextShadow->ShadowAt(i);
+    nsMargin blur = nsContextBoxBlur::GetBlurRadiusMargin(shadow->mRadius, A2D);
+    if ((aFlags & EXCLUDE_BLUR_SHADOWS) && blur != nsMargin(0, 0, 0, 0))
+      continue;
+
+    nsRect tmpRect(aTextAndDecorationsRect);
+
+    tmpRect.MoveBy(nsPoint(shadow->mXOffset, shadow->mYOffset));
+    tmpRect.Inflate(blur);
+
+    resultRect.UnionRect(resultRect, tmpRect);
+  }
+  return resultRect;
+}
+
+enum ObjectDimensionType { eWidth, eHeight };
+static nscoord
+ComputeMissingDimension(const nsSize& aDefaultObjectSize,
+                        const nsSize& aIntrinsicRatio,
+                        const Maybe<nscoord>& aSpecifiedWidth,
+                        const Maybe<nscoord>& aSpecifiedHeight,
+                        ObjectDimensionType aDimensionToCompute)
+{
+  // The "default sizing algorithm" computes the missing dimension as follows:
+  // (source: http://dev.w3.org/csswg/css-images-3/#default-sizing )
+
+  // 1. "If the object has an intrinsic aspect ratio, the missing dimension of
+  //     the concrete object size is calculated using the intrinsic aspect
+  //     ratio and the present dimension."
+  if (aIntrinsicRatio.width > 0 && aIntrinsicRatio.height > 0) {
+    // Fill in the missing dimension using the intrinsic aspect ratio.
+    nscoord knownDimensionSize;
+    float ratio;
+    if (aDimensionToCompute == eWidth) {
+      knownDimensionSize = *aSpecifiedHeight;
+      ratio = aIntrinsicRatio.width / aIntrinsicRatio.height;
+    } else {
+      knownDimensionSize = *aSpecifiedWidth;
+      ratio = aIntrinsicRatio.height / aIntrinsicRatio.width;
+    }
+    return NSCoordSaturatingNonnegativeMultiply(knownDimensionSize, ratio);
+  }
+
+  // 2. "Otherwise, if the missing dimension is present in the object’s
+  //     intrinsic dimensions, [...]"
+  // NOTE: *Skipping* this case, because we already know it's not true -- we're
+  // in this function because the missing dimension is *not* present in
+  // the object's intrinsic dimensions.
+
+  // 3. "Otherwise, the missing dimension of the concrete object size is taken
+  //     from the default object size. "
+  return (aDimensionToCompute == eWidth) ?
+    aDefaultObjectSize.width : aDefaultObjectSize.height;
+}
+
+/*
+ * This computes & returns the concrete object size of replaced content, if
+ * that content were to be rendered with "object-fit: none".  (Or, if the
+ * element has neither an intrinsic height nor width, this method returns an
+ * empty Maybe<> object.)
+ *
+ * As specced...
+ *   http://dev.w3.org/csswg/css-images-3/#valdef-object-fit-none
+ * ..we use "the default sizing algorithm with no specified size,
+ * and a default object size equal to the replaced element's used width and
+ * height."
+ *
+ * The default sizing algorithm is described here:
+ *   http://dev.w3.org/csswg/css-images-3/#default-sizing
+ * Quotes in the function-impl are taken from that ^ spec-text.
+ *
+ * Per its final bulleted section: since there's no specified size,
+ * we run the default sizing algorithm using the object's intrinsic size in
+ * place of the specified size. But if the object has neither an intrinsic
+ * height nor an intrinsic width, then we instead return without populating our
+ * outparam, and we let the caller figure out the size (using a contain
+ * constraint).
+ */
+static Maybe<nsSize>
+MaybeComputeObjectFitNoneSize(const nsSize& aDefaultObjectSize,
+                              const IntrinsicSize& aIntrinsicSize,
+                              const nsSize& aIntrinsicRatio)
+{
+  // "If the object has an intrinsic height or width, its size is resolved as
+  // if its intrinsic dimensions were given as the specified size."
+  //
+  // So, first we check if we have an intrinsic height and/or width:
+  Maybe<nscoord> specifiedWidth;
+  if (aIntrinsicSize.width.GetUnit() == eStyleUnit_Coord) {
+    specifiedWidth.emplace(aIntrinsicSize.width.GetCoordValue());
+  }
+
+  Maybe<nscoord> specifiedHeight;
+  if (aIntrinsicSize.height.GetUnit() == eStyleUnit_Coord) {
+    specifiedHeight.emplace(aIntrinsicSize.height.GetCoordValue());
+  }
+
+  Maybe<nsSize> noneSize; // (the value we'll return)
+  if (specifiedWidth || specifiedHeight) {
+    // We have at least one specified dimension; use whichever dimension is
+    // specified, and compute the other one using our intrinsic ratio, or (if
+    // no valid ratio) using the default object size.
+    noneSize.emplace();
+
+    noneSize->width = specifiedWidth ?
+      *specifiedWidth :
+      ComputeMissingDimension(aDefaultObjectSize, aIntrinsicRatio,
+                              specifiedWidth, specifiedHeight,
+                              eWidth);
+
+    noneSize->height = specifiedHeight ?
+      *specifiedHeight :
+      ComputeMissingDimension(aDefaultObjectSize, aIntrinsicRatio,
+                              specifiedWidth, specifiedHeight,
+                              eHeight);
+  }
+  // [else:] "Otherwise [if there's neither an intrinsic height nor width], its
+  // size is resolved as a contain constraint against the default object size."
+  // We'll let our caller do that, to share code & avoid redundant
+  // computations; so, we return w/out populating noneSize.
+  return noneSize;
+}
+
+// Computes the concrete object size to render into, as described at
+// http://dev.w3.org/csswg/css-images-3/#concrete-size-resolution
+static nsSize
+ComputeConcreteObjectSize(const nsSize& aConstraintSize,
+                          const IntrinsicSize& aIntrinsicSize,
+                          const nsSize& aIntrinsicRatio,
+                          uint8_t aObjectFit)
+{
+  // Handle default behavior (filling the container) w/ fast early return.
+  // (Also: if there's no valid intrinsic ratio, then we have the "fill"
+  // behavior & just use the constraint size.)
+  if (MOZ_LIKELY(aObjectFit == NS_STYLE_OBJECT_FIT_FILL) ||
+      aIntrinsicRatio.width == 0 ||
+      aIntrinsicRatio.height == 0) {
+    return aConstraintSize;
+  }
+
+  // The type of constraint to compute (cover/contain), if needed:
+  Maybe<nsImageRenderer::FitType> fitType;
+
+  Maybe<nsSize> noneSize;
+  if (aObjectFit == NS_STYLE_OBJECT_FIT_NONE ||
+      aObjectFit == NS_STYLE_OBJECT_FIT_SCALE_DOWN) {
+    noneSize = MaybeComputeObjectFitNoneSize(aConstraintSize, aIntrinsicSize,
+                                             aIntrinsicRatio);
+    if (!noneSize || aObjectFit == NS_STYLE_OBJECT_FIT_SCALE_DOWN) {
+      // Need to compute a 'CONTAIN' constraint (either for the 'none' size
+      // itself, or for comparison w/ the 'none' size to resolve 'scale-down'.)
+      fitType.emplace(nsImageRenderer::CONTAIN);
+    }
+  } else if (aObjectFit == NS_STYLE_OBJECT_FIT_COVER) {
+    fitType.emplace(nsImageRenderer::COVER);
+  } else if (aObjectFit == NS_STYLE_OBJECT_FIT_CONTAIN) {
+    fitType.emplace(nsImageRenderer::CONTAIN);
+  }
+
+  Maybe<nsSize> constrainedSize;
+  if (fitType) {
+    constrainedSize.emplace(
+      nsImageRenderer::ComputeConstrainedSize(aConstraintSize,
+                                              aIntrinsicRatio,
+                                              *fitType));
+  }
+
+  // Now, we should have all the sizing information that we need.
+  switch (aObjectFit) {
+    // skipping NS_STYLE_OBJECT_FIT_FILL; we handled it w/ early-return.
+    case NS_STYLE_OBJECT_FIT_CONTAIN:
+    case NS_STYLE_OBJECT_FIT_COVER:
+      MOZ_ASSERT(constrainedSize);
+      return *constrainedSize;
+
+    case NS_STYLE_OBJECT_FIT_NONE:
+      if (noneSize) {
+        return *noneSize;
+      }
+      MOZ_ASSERT(constrainedSize);
+      return *constrainedSize;
+
+    case NS_STYLE_OBJECT_FIT_SCALE_DOWN:
+      MOZ_ASSERT(constrainedSize);
+      if (noneSize) {
+        constrainedSize->width =
+          std::min(constrainedSize->width, noneSize->width);
+        constrainedSize->height =
+          std::min(constrainedSize->height, noneSize->height);
+      }
+      return *constrainedSize;
+
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unexpected enum value for 'object-fit'");
+      return aConstraintSize; // fall back to (default) 'fill' behavior
+  }
+}
+
+// (Helper for HasInitialObjectFitAndPosition, to check
+// each "object-position" coord.)
+static bool
+IsCoord50Pct(const mozilla::Position::Coord& aCoord)
+{
+  return (aCoord.mLength == 0 &&
+          aCoord.mHasPercent &&
+          aCoord.mPercent == 0.5f);
+}
+
+// Indicates whether the given nsStylePosition has the initial values
+// for the "object-fit" and "object-position" properties.
+static bool
+HasInitialObjectFitAndPosition(const nsStylePosition* aStylePos)
+{
+  const mozilla::Position& objectPos = aStylePos->mObjectPosition;
+
+  return aStylePos->mObjectFit == NS_STYLE_OBJECT_FIT_FILL &&
+    IsCoord50Pct(objectPos.mXPosition) &&
+    IsCoord50Pct(objectPos.mYPosition);
+}
+
+/* static */ nsRect
+nsLayoutUtils::ComputeObjectDestRect(const nsRect& aConstraintRect,
+                                     const IntrinsicSize& aIntrinsicSize,
+                                     const nsSize& aIntrinsicRatio,
+                                     const nsStylePosition* aStylePos,
+                                     nsPoint* aAnchorPoint)
+{
+  // Step 1: Figure out our "concrete object size"
+  // (the size of the region we'll actually draw our image's pixels into).
+  nsSize concreteObjectSize =
+    ComputeConcreteObjectSize(aConstraintRect.Size(), aIntrinsicSize,
+                              aIntrinsicRatio, aStylePos->mObjectFit);
+
+  // Step 2: Figure out how to align that region in the element's content-box.
+  nsPoint imageTopLeftPt, imageAnchorPt;
+  nsImageRenderer::ComputeObjectAnchorPoint(aStylePos->mObjectPosition,
+                                            aConstraintRect.Size(),
+                                            concreteObjectSize,
+                                            &imageTopLeftPt, &imageAnchorPt);
+  // Right now, we're with respect to aConstraintRect's top-left point.  We add
+  // that point here, to convert to the same broader coordinate space that
+  // aConstraintRect is in.
+  imageTopLeftPt += aConstraintRect.TopLeft();
+  imageAnchorPt += aConstraintRect.TopLeft();
+
+  if (aAnchorPoint) {
+    // Special-case: if our "object-fit" and "object-position" properties have
+    // their default values ("object-fit: fill; object-position:50% 50%"), then
+    // we'll override the calculated imageAnchorPt, and instead use the
+    // object's top-left corner.
+    //
+    // This special case is partly for backwards compatibility (since
+    // traditionally we've pixel-aligned the top-left corner of e.g. <img>
+    // elements), and partly because ComputeSnappedDrawingParameters produces
+    // less error if the anchor point is at the top-left corner. So, all other
+    // things being equal, we prefer that code path with less error.
+    if (HasInitialObjectFitAndPosition(aStylePos)) {
+      *aAnchorPoint = imageTopLeftPt;
+    } else {
+      *aAnchorPoint = imageAnchorPt;
+    }
+  }
+  return nsRect(imageTopLeftPt, concreteObjectSize);
+}
+
+already_AddRefed<nsFontMetrics>
+nsLayoutUtils::GetFontMetricsForFrame(const nsIFrame* aFrame, float aInflation)
+{
+  nsStyleContext* styleContext = aFrame->StyleContext();
+  uint8_t variantWidth = NS_FONT_VARIANT_WIDTH_NORMAL;
+  if (styleContext->IsTextCombined()) {
+    MOZ_ASSERT(aFrame->GetType() == nsGkAtoms::textFrame);
+    auto textFrame = static_cast<const nsTextFrame*>(aFrame);
+    auto clusters = textFrame->CountGraphemeClusters();
+    if (clusters == 2) {
+      variantWidth = NS_FONT_VARIANT_WIDTH_HALF;
+    } else if (clusters == 3) {
+      variantWidth = NS_FONT_VARIANT_WIDTH_THIRD;
+    } else if (clusters == 4) {
+      variantWidth = NS_FONT_VARIANT_WIDTH_QUARTER;
+    }
+  }
+  return GetFontMetricsForStyleContext(styleContext, aInflation, variantWidth);
+}
+
+already_AddRefed<nsFontMetrics>
+nsLayoutUtils::GetFontMetricsForStyleContext(nsStyleContext* aStyleContext,
+                                             float aInflation,
+                                             uint8_t aVariantWidth)
+{
+  nsPresContext* pc = aStyleContext->PresContext();
+
+  WritingMode wm(aStyleContext);
+  const nsStyleFont* styleFont = aStyleContext->StyleFont();
+  nsFontMetrics::Params params;
+  params.language = styleFont->mLanguage;
+  params.explicitLanguage = styleFont->mExplicitLanguage;
+  params.orientation =
+    wm.IsVertical() && !wm.IsSideways() ? gfxFont::eVertical
+                                        : gfxFont::eHorizontal;
+  // pass the user font set object into the device context to
+  // pass along to CreateFontGroup
+  params.userFontSet = pc->GetUserFontSet();
+  params.textPerf = pc->GetTextPerfMetrics();
+
+  // When aInflation is 1.0 and we don't require width variant, avoid
+  // making a local copy of the nsFont.
+  // This also avoids running font.size through floats when it is large,
+  // which would be lossy.  Fortunately, in such cases, aInflation is
+  // guaranteed to be 1.0f.
+  if (aInflation == 1.0f && aVariantWidth == NS_FONT_VARIANT_WIDTH_NORMAL) {
+    return pc->DeviceContext()->GetMetricsFor(styleFont->mFont, params);
+  }
+
+  nsFont font = styleFont->mFont;
+  font.size = NSToCoordRound(font.size * aInflation);
+  font.variantWidth = aVariantWidth;
+  return pc->DeviceContext()->GetMetricsFor(font, params);
+}
+
+nsIFrame*
+nsLayoutUtils::FindChildContainingDescendant(nsIFrame* aParent, nsIFrame* aDescendantFrame)
+{
+  nsIFrame* result = aDescendantFrame;
+
+  while (result) {
+    nsIFrame* parent = result->GetParent();
+    if (parent == aParent) {
+      break;
+    }
+
+    // The frame is not an immediate child of aParent so walk up another level
+    result = parent;
+  }
+
+  return result;
+}
+
+nsBlockFrame*
+nsLayoutUtils::GetAsBlock(nsIFrame* aFrame)
+{
+  nsBlockFrame* block = do_QueryFrame(aFrame);
+  return block;
+}
+
+nsBlockFrame*
+nsLayoutUtils::FindNearestBlockAncestor(nsIFrame* aFrame)
+{
+  nsIFrame* nextAncestor;
+  for (nextAncestor = aFrame->GetParent(); nextAncestor;
+       nextAncestor = nextAncestor->GetParent()) {
+    nsBlockFrame* block = GetAsBlock(nextAncestor);
+    if (block)
+      return block;
+  }
+  return nullptr;
+}
+
+nsIFrame*
+nsLayoutUtils::GetNonGeneratedAncestor(nsIFrame* aFrame)
+{
+  if (!(aFrame->GetStateBits() & NS_FRAME_GENERATED_CONTENT))
+    return aFrame;
+
+  nsIFrame* f = aFrame;
+  do {
+    f = GetParentOrPlaceholderFor(f);
+  } while (f->GetStateBits() & NS_FRAME_GENERATED_CONTENT);
+  return f;
+}
+
+nsIFrame*
+nsLayoutUtils::GetParentOrPlaceholderFor(nsIFrame* aFrame)
+{
+  if ((aFrame->GetStateBits() & NS_FRAME_OUT_OF_FLOW)
+      && !aFrame->GetPrevInFlow()) {
+    return aFrame->PresContext()->PresShell()->FrameManager()->
+      GetPlaceholderFrameFor(aFrame);
+  }
+  return aFrame->GetParent();
+}
+
+nsIFrame*
+nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(nsIFrame* aFrame)
+{
+  nsIFrame* f = GetParentOrPlaceholderFor(aFrame);
+  if (f)
+    return f;
+  return GetCrossDocParentFrame(aFrame);
+}
+
+nsIFrame*
+nsLayoutUtils::GetNextContinuationOrIBSplitSibling(nsIFrame *aFrame)
+{
+  nsIFrame *result = aFrame->GetNextContinuation();
+  if (result)
+    return result;
+
+  if ((aFrame->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT) != 0) {
+    // We only store the ib-split sibling annotation with the first
+    // frame in the continuation chain. Walk back to find that frame now.
+    aFrame = aFrame->FirstContinuation();
+
+    return aFrame->Properties().Get(nsIFrame::IBSplitSibling());
+  }
+
+  return nullptr;
+}
+
+nsIFrame*
+nsLayoutUtils::FirstContinuationOrIBSplitSibling(nsIFrame *aFrame)
+{
+  nsIFrame *result = aFrame->FirstContinuation();
+  if (result->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT) {
+    while (true) {
+      nsIFrame* f =
+        result->Properties().Get(nsIFrame::IBSplitPrevSibling());
+      if (!f)
+        break;
+      result = f;
+    }
+  }
+
+  return result;
+}
+
+nsIFrame*
+nsLayoutUtils::LastContinuationOrIBSplitSibling(nsIFrame *aFrame)
+{
+  nsIFrame *result = aFrame->FirstContinuation();
+  if (result->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT) {
+    while (true) {
+      nsIFrame* f =
+        result->Properties().Get(nsIFrame::IBSplitSibling());
+      if (!f)
+        break;
+      result = f;
+    }
+  }
+
+  result = result->LastContinuation();
+
+  return result;
+}
+
+bool
+nsLayoutUtils::IsFirstContinuationOrIBSplitSibling(nsIFrame *aFrame)
+{
+  if (aFrame->GetPrevContinuation()) {
+    return false;
+  }
+  if ((aFrame->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT) &&
+      aFrame->Properties().Get(nsIFrame::IBSplitPrevSibling())) {
+    return false;
+  }
+
+  return true;
+}
+
+bool
+nsLayoutUtils::IsViewportScrollbarFrame(nsIFrame* aFrame)
+{
+  if (!aFrame)
+    return false;
+
+  nsIFrame* rootScrollFrame =
+    aFrame->PresContext()->PresShell()->GetRootScrollFrame();
+  if (!rootScrollFrame)
+    return false;
+
+  nsIScrollableFrame* rootScrollableFrame = do_QueryFrame(rootScrollFrame);
+  NS_ASSERTION(rootScrollableFrame, "The root scorollable frame is null");
+
+  if (!IsProperAncestorFrame(rootScrollFrame, aFrame))
+    return false;
+
+  nsIFrame* rootScrolledFrame = rootScrollableFrame->GetScrolledFrame();
+  return !(rootScrolledFrame == aFrame ||
+           IsProperAncestorFrame(rootScrolledFrame, aFrame));
+}
+
+// Use only for widths/heights (or their min/max), since it clamps
+// negative calc() results to 0.
+static bool GetAbsoluteCoord(const nsStyleCoord& aStyle, nscoord& aResult)
+{
+  if (aStyle.IsCalcUnit()) {
+    if (aStyle.CalcHasPercent()) {
+      return false;
+    }
+    // If it has no percents, we can pass 0 for the percentage basis.
+    aResult = nsRuleNode::ComputeComputedCalc(aStyle, 0);
+    if (aResult < 0)
+      aResult = 0;
+    return true;
+  }
+
+  if (eStyleUnit_Coord != aStyle.GetUnit())
+    return false;
+
+  aResult = aStyle.GetCoordValue();
+  NS_ASSERTION(aResult >= 0, "negative widths not allowed");
+  return true;
+}
+
+static nscoord
+GetBSizeTakenByBoxSizing(StyleBoxSizing aBoxSizing,
+                         nsIFrame* aFrame,
+                         bool aHorizontalAxis,
+                         bool aIgnorePadding);
+
+// Only call on style coords for which GetAbsoluteCoord returned false.
+static bool
+GetPercentBSize(const nsStyleCoord& aStyle,
+                nsIFrame* aFrame,
+                bool aHorizontalAxis,
+                nscoord& aResult)
+{
+  if (eStyleUnit_Percent != aStyle.GetUnit() &&
+      !aStyle.IsCalcUnit())
+    return false;
+
+  MOZ_ASSERT(!aStyle.IsCalcUnit() || aStyle.CalcHasPercent(),
+             "GetAbsoluteCoord should have handled this");
+
+  // During reflow, nsHTMLScrollFrame::ReflowScrolledFrame uses
+  // SetComputedHeight on the reflow state for its child to propagate its
+  // computed height to the scrolled content. So here we skip to the scroll
+  // frame that contains this scrolled content in order to get the same
+  // behavior as layout when computing percentage heights.
+  nsIFrame *f = aFrame->GetContainingBlock(nsIFrame::SKIP_SCROLLED_FRAME);
+  if (!f) {
+    NS_NOTREACHED("top of frame tree not a containing block");
+    return false;
+  }
+
+  WritingMode wm = f->GetWritingMode();
+
+  const nsStylePosition *pos = f->StylePosition();
+  const nsStyleCoord& bSizeCoord = pos->BSize(wm);
+  nscoord h;
+  if (!GetAbsoluteCoord(bSizeCoord, h) &&
+      !GetPercentBSize(bSizeCoord, f, aHorizontalAxis, h)) {
+    NS_ASSERTION(bSizeCoord.GetUnit() == eStyleUnit_Auto ||
+                 bSizeCoord.HasPercent(),
+                 "unknown block-size unit");
+    nsIAtom* fType = f->GetType();
+    if (fType != nsGkAtoms::viewportFrame && fType != nsGkAtoms::canvasFrame &&
+        fType != nsGkAtoms::pageContentFrame) {
+      // There's no basis for the percentage height, so it acts like auto.
+      // Should we consider a max-height < min-height pair a basis for
+      // percentage heights?  The spec is somewhat unclear, and not doing
+      // so is simpler and avoids troubling discontinuities in behavior,
+      // so I'll choose not to. -LDB
+      return false;
+    }
+
+    NS_ASSERTION(bSizeCoord.GetUnit() == eStyleUnit_Auto,
+                 "Unexpected block-size unit for viewport or canvas or page-content");
+    // For the viewport, canvas, and page-content kids, the percentage
+    // basis is just the parent block-size.
+    h = f->BSize(wm);
+    if (h == NS_UNCONSTRAINEDSIZE) {
+      // We don't have a percentage basis after all
+      return false;
+    }
+  }
+
+  const nsStyleCoord& maxBSizeCoord = pos->MaxBSize(wm);
+
+  nscoord maxh;
+  if (GetAbsoluteCoord(maxBSizeCoord, maxh) ||
+      GetPercentBSize(maxBSizeCoord, f, aHorizontalAxis, maxh)) {
+    if (maxh < h)
+      h = maxh;
+  } else {
+    NS_ASSERTION(maxBSizeCoord.GetUnit() == eStyleUnit_None ||
+                 maxBSizeCoord.HasPercent(),
+                 "unknown max block-size unit");
+  }
+
+  const nsStyleCoord& minBSizeCoord = pos->MinBSize(wm);
+
+  nscoord minh;
+  if (GetAbsoluteCoord(minBSizeCoord, minh) ||
+      GetPercentBSize(minBSizeCoord, f, aHorizontalAxis, minh)) {
+    if (minh > h)
+      h = minh;
+  } else {
+    NS_ASSERTION(minBSizeCoord.HasPercent() ||
+                 minBSizeCoord.GetUnit() == eStyleUnit_Auto,
+                 "unknown min block-size unit");
+  }
+
+  // Now adjust h for box-sizing styles on the parent.  We never ignore padding
+  // here.  That could conceivably cause some problems with fieldsets (which are
+  // the one place that wants to ignore padding), but solving that here without
+  // hardcoding a check for f being a fieldset-content frame is a bit of a pain.
+  nscoord bSizeTakenByBoxSizing =
+    GetBSizeTakenByBoxSizing(pos->mBoxSizing, f, aHorizontalAxis, false);
+  h = std::max(0, h - bSizeTakenByBoxSizing);
+
+  if (aStyle.IsCalcUnit()) {
+    aResult = std::max(nsRuleNode::ComputeComputedCalc(aStyle, h), 0);
+    return true;
+  }
+
+  aResult = NSToCoordRound(aStyle.GetPercentValue() * h);
+  return true;
+}
+
+// Get the amount of vertical space taken out of aFrame's content area due to
+// its borders and paddings given the box-sizing value in aBoxSizing.  We don't
+// get aBoxSizing from the frame because some callers want to compute this for
+// specific box-sizing values.  aHorizontalAxis is true if our inline direction
+// is horisontal and our block direction is vertical.  aIgnorePadding is true if
+// padding should be ignored.
+static nscoord
+GetBSizeTakenByBoxSizing(StyleBoxSizing aBoxSizing,
+                         nsIFrame* aFrame,
+                         bool aHorizontalAxis,
+                         bool aIgnorePadding)
+{
+  nscoord bSizeTakenByBoxSizing = 0;
+  if (aBoxSizing == StyleBoxSizing::Border) {
+    const nsStyleBorder* styleBorder = aFrame->StyleBorder();
+    bSizeTakenByBoxSizing +=
+      aHorizontalAxis ? styleBorder->GetComputedBorder().TopBottom()
+                      : styleBorder->GetComputedBorder().LeftRight();
+    if (!aIgnorePadding) {
+      const nsStyleSides& stylePadding =
+        aFrame->StylePadding()->mPadding;
+      const nsStyleCoord& paddingStart =
+        stylePadding.Get(aHorizontalAxis ? NS_SIDE_TOP : NS_SIDE_LEFT);
+      const nsStyleCoord& paddingEnd =
+        stylePadding.Get(aHorizontalAxis ? NS_SIDE_BOTTOM : NS_SIDE_RIGHT);
+      nscoord pad;
+      // XXXbz Calling GetPercentBSize on padding values looks bogus, since
+      // percent padding is always a percentage of the inline-size of the
+      // containing block.  We should perhaps just treat non-absolute paddings
+      // here as 0 instead, except that in some cases the width may in fact be
+      // known.  See bug 1231059.
+      if (GetAbsoluteCoord(paddingStart, pad) ||
+          GetPercentBSize(paddingStart, aFrame, aHorizontalAxis, pad)) {
+        bSizeTakenByBoxSizing += pad;
+      }
+      if (GetAbsoluteCoord(paddingEnd, pad) ||
+          GetPercentBSize(paddingEnd, aFrame, aHorizontalAxis, pad)) {
+        bSizeTakenByBoxSizing += pad;
+      }
+    }
+  }
+  return bSizeTakenByBoxSizing;
+}
+
+// Handles only -moz-max-content and -moz-min-content, and
+// -moz-fit-content for min-width and max-width, since the others
+// (-moz-fit-content for width, and -moz-available) have no effect on
+// intrinsic widths.
+enum eWidthProperty { PROP_WIDTH, PROP_MAX_WIDTH, PROP_MIN_WIDTH };
+static bool
+GetIntrinsicCoord(const nsStyleCoord& aStyle,
+                  nsRenderingContext* aRenderingContext,
+                  nsIFrame* aFrame,
+                  eWidthProperty aProperty,
+                  nscoord& aResult)
+{
+  NS_PRECONDITION(aProperty == PROP_WIDTH || aProperty == PROP_MAX_WIDTH ||
+                  aProperty == PROP_MIN_WIDTH, "unexpected property");
+  if (aStyle.GetUnit() != eStyleUnit_Enumerated)
+    return false;
+  int32_t val = aStyle.GetIntValue();
+  NS_ASSERTION(val == NS_STYLE_WIDTH_MAX_CONTENT ||
+               val == NS_STYLE_WIDTH_MIN_CONTENT ||
+               val == NS_STYLE_WIDTH_FIT_CONTENT ||
+               val == NS_STYLE_WIDTH_AVAILABLE,
+               "unexpected enumerated value for width property");
+  if (val == NS_STYLE_WIDTH_AVAILABLE)
+    return false;
+  if (val == NS_STYLE_WIDTH_FIT_CONTENT) {
+    if (aProperty == PROP_WIDTH)
+      return false; // handle like 'width: auto'
+    if (aProperty == PROP_MAX_WIDTH)
+      // constrain large 'width' values down to -moz-max-content
+      val = NS_STYLE_WIDTH_MAX_CONTENT;
+    else
+      // constrain small 'width' or 'max-width' values up to -moz-min-content
+      val = NS_STYLE_WIDTH_MIN_CONTENT;
+  }
+
+  NS_ASSERTION(val == NS_STYLE_WIDTH_MAX_CONTENT ||
+               val == NS_STYLE_WIDTH_MIN_CONTENT,
+               "should have reduced everything remaining to one of these");
+
+  // If aFrame is a container for font size inflation, then shrink
+  // wrapping inside of it should not apply font size inflation.
+  AutoMaybeDisableFontInflation an(aFrame);
+
+  if (val == NS_STYLE_WIDTH_MAX_CONTENT)
+    aResult = aFrame->GetPrefISize(aRenderingContext);
+  else
+    aResult = aFrame->GetMinISize(aRenderingContext);
+  return true;
+}
+
+#undef  DEBUG_INTRINSIC_WIDTH
+
+#ifdef DEBUG_INTRINSIC_WIDTH
+static int32_t gNoiseIndent = 0;
+#endif
+
+// Return true for form controls whose minimum intrinsic inline-size
+// shrinks to 0 when they have a percentage inline-size (but not
+// percentage max-inline-size).  (Proper replaced elements, whose
+// intrinsic minimium inline-size shrinks to 0 for both percentage
+// inline-size and percentage max-inline-size, are handled elsewhere.)
+inline static bool
+FormControlShrinksForPercentISize(nsIFrame* aFrame)
+{
+  if (!aFrame->IsFrameOfType(nsIFrame::eReplaced)) {
+    // Quick test to reject most frames.
+    return false;
+  }
+
+  nsIAtom* fType = aFrame->GetType();
+  if (fType == nsGkAtoms::meterFrame || fType == nsGkAtoms::progressFrame) {
+    // progress and meter do have this shrinking behavior
+    // FIXME: Maybe these should be nsIFormControlFrame?
+    return true;
+  }
+
+  if (!static_cast<nsIFormControlFrame*>(do_QueryFrame(aFrame))) {
+    // Not a form control.  This includes fieldsets, which do not
+    // shrink.
+    return false;
+  }
+
+  if (fType == nsGkAtoms::gfxButtonControlFrame ||
+      fType == nsGkAtoms::HTMLButtonControlFrame) {
+    // Buttons don't have this shrinking behavior.  (Note that color
+    // inputs do, even though they inherit from button, so we can't use
+    // do_QueryFrame here.)
+    return false;
+  }
+
+  return true;
+}
+
+/**
+ * Add aOffsets which describes what to add on outside of the content box
+ * aContentSize (controlled by 'box-sizing') and apply min/max properties.
+ * We have to account for these properties after getting all the offsets
+ * (margin, border, padding) because percentages do not operate linearly.
+ * Doing this is ok because although percentages aren't handled linearly,
+ * they are handled monotonically.
+ *
+ * @param aContentSize the content size calculated so far
+                       (@see IntrinsicForContainer)
+ * @param aContentMinSize ditto min content size
+ * @param aStyleSize a 'width' or 'height' property value
+ * @param aFixedMinSize if aStyleMinSize is a definite size then this points to
+ *                      the value, otherwise nullptr
+ * @param aStyleMinSize a 'min-width' or 'min-height' property value
+ * @param aFixedMaxSize if aStyleMaxSize is a definite size then this points to
+ *                      the value, otherwise nullptr
+ * @param aStyleMaxSize a 'max-width' or 'max-height' property value
+ * @param aFlags same as for IntrinsicForContainer
+ * @param aContainerWM the container's WM
+ */
+static nscoord
+AddIntrinsicSizeOffset(nsRenderingContext* aRenderingContext,
+                       nsIFrame* aFrame,
+                       const nsIFrame::IntrinsicISizeOffsetData& aOffsets,
+                       nsLayoutUtils::IntrinsicISizeType aType,
+                       StyleBoxSizing aBoxSizing,
+                       nscoord aContentSize,
+                       nscoord aContentMinSize,
+                       const nsStyleCoord& aStyleSize,
+                       const nscoord* aFixedMinSize,
+                       const nsStyleCoord& aStyleMinSize,
+                       const nscoord* aFixedMaxSize,
+                       const nsStyleCoord& aStyleMaxSize,
+                       uint32_t aFlags,
+                       PhysicalAxis aAxis)
+{
+  nscoord result = aContentSize;
+  nscoord min = aContentMinSize;
+  nscoord coordOutsideSize = 0;
+  float pctOutsideSize = 0;
+  float pctTotal = 0.0f;
+
+  if (!(aFlags & nsLayoutUtils::IGNORE_PADDING)) {
+    coordOutsideSize += aOffsets.hPadding;
+    pctOutsideSize += aOffsets.hPctPadding;
+  }
+
+  coordOutsideSize += aOffsets.hBorder;
+
+  if (aBoxSizing == StyleBoxSizing::Border) {
+    min += coordOutsideSize;
+    result = NSCoordSaturatingAdd(result, coordOutsideSize);
+    pctTotal += pctOutsideSize;
+
+    coordOutsideSize = 0;
+    pctOutsideSize = 0.0f;
+  }
+
+  coordOutsideSize += aOffsets.hMargin;
+  pctOutsideSize += aOffsets.hPctMargin;
+
+  min += coordOutsideSize;
+  result = NSCoordSaturatingAdd(result, coordOutsideSize);
+  pctTotal += pctOutsideSize;
+
+  const bool shouldAddPercent = aType == nsLayoutUtils::PREF_ISIZE ||
+                                (aFlags & nsLayoutUtils::ADD_PERCENTS);
+  nscoord size;
+  if (aType == nsLayoutUtils::MIN_ISIZE &&
+      (((aStyleSize.HasPercent() || aStyleMaxSize.HasPercent()) &&
+        aFrame->IsFrameOfType(nsIFrame::eReplacedSizing)) ||
+       (aStyleSize.HasPercent() &&
+        FormControlShrinksForPercentISize(aFrame)))) {
+    // A percentage width or max-width on replaced elements means they
+    // can shrink to 0.
+    // This is also true for percentage widths (but not max-widths) on
+    // text inputs.
+    // Note that if this is max-width, this overrides the fixed-width
+    // rule in the next condition.
+    result = 0; // let |min| handle padding/border/margin
+  } else if (GetAbsoluteCoord(aStyleSize, size) ||
+             GetIntrinsicCoord(aStyleSize, aRenderingContext, aFrame,
+                               PROP_WIDTH, size)) {
+    result = size + coordOutsideSize;
+    if (shouldAddPercent) {
+      result = nsLayoutUtils::AddPercents(result, pctOutsideSize);
+    }
+  } else {
+    // NOTE: We could really do a lot better for percents and for some
+    // cases of calc() containing percent (certainly including any where
+    // the coefficient on the percent is positive and there are no max()
+    // expressions).  However, doing better for percents wouldn't be
+    // backwards compatible.
+    if (shouldAddPercent) {
+      result = nsLayoutUtils::AddPercents(result, pctTotal);
+    }
+  }
+
+  nscoord maxSize = aFixedMaxSize ? *aFixedMaxSize : 0;
+  if (aFixedMaxSize ||
+      GetIntrinsicCoord(aStyleMaxSize, aRenderingContext, aFrame,
+                        PROP_MAX_WIDTH, maxSize)) {
+    maxSize += coordOutsideSize;
+    if (shouldAddPercent) {
+      maxSize = nsLayoutUtils::AddPercents(maxSize, pctOutsideSize);
+    }
+    if (result > maxSize) {
+      result = maxSize;
+    }
+  }
+
+  nscoord minSize = aFixedMinSize ? *aFixedMinSize : 0;
+  if (aFixedMinSize ||
+      GetIntrinsicCoord(aStyleMinSize, aRenderingContext, aFrame,
+                        PROP_MIN_WIDTH, minSize)) {
+    minSize += coordOutsideSize;
+    if (shouldAddPercent) {
+      minSize = nsLayoutUtils::AddPercents(minSize, pctOutsideSize);
+    }
+    if (result < minSize) {
+      result = minSize;
+    }
+  }
+
+  if (shouldAddPercent) {
+    min = nsLayoutUtils::AddPercents(min, pctTotal);
+  }
+  if (result < min) {
+    result = min;
+  }
+
+  const nsStyleDisplay* disp = aFrame->StyleDisplay();
+  if (aFrame->IsThemed(disp)) {
+    LayoutDeviceIntSize devSize;
+    bool canOverride = true;
+    nsPresContext* pc = aFrame->PresContext();
+    pc->GetTheme()->GetMinimumWidgetSize(pc, aFrame, disp->mAppearance,
+                                         &devSize, &canOverride);
+    nscoord themeSize =
+      pc->DevPixelsToAppUnits(aAxis == eAxisVertical ? devSize.height
+                                                     : devSize.width);
+    // GetMinimumWidgetSize() returns a border-box width.
+    themeSize += aOffsets.hMargin;
+    if (shouldAddPercent) {
+      themeSize = nsLayoutUtils::AddPercents(themeSize, aOffsets.hPctMargin);
+    }
+    if (themeSize > result || !canOverride) {
+      result = themeSize;
+    }
+  }
+  return result;
+}
+
+static void
+AddStateBitToAncestors(nsIFrame* aFrame, nsFrameState aBit)
+{
+  for (nsIFrame* f = aFrame; f; f = f->GetParent()) {
+    if (f->HasAnyStateBits(aBit)) {
+      break;
+    }
+    f->AddStateBits(aBit);
+  }
+}
+
+/* static */ nscoord
+nsLayoutUtils::IntrinsicForAxis(PhysicalAxis        aAxis,
+                                nsRenderingContext* aRenderingContext,
+                                nsIFrame*           aFrame,
+                                IntrinsicISizeType  aType,
+                                uint32_t            aFlags,
+                                nscoord             aMarginBoxMinSizeClamp)
+{
+  NS_PRECONDITION(aFrame, "null frame");
+  NS_PRECONDITION(aFrame->GetParent(),
+                  "IntrinsicForAxis called on frame not in tree");
+  NS_PRECONDITION(aType == MIN_ISIZE || aType == PREF_ISIZE, "bad type");
+
+  const bool horizontalAxis = MOZ_LIKELY(aAxis == eAxisHorizontal);
+#ifdef DEBUG_INTRINSIC_WIDTH
+  nsFrame::IndentBy(stderr, gNoiseIndent);
+  static_cast<nsFrame*>(aFrame)->ListTag(stderr);
+  printf_stderr(" %s %s intrinsic size for container:\n",
+                aType == MIN_ISIZE ? "min" : "pref",
+                horizontalAxis ? "horizontal" : "vertical");
+#endif
+
+  // If aFrame is a container for font size inflation, then shrink
+  // wrapping inside of it should not apply font size inflation.
+  AutoMaybeDisableFontInflation an(aFrame);
+
+  // We want the size this frame will contribute to the parent's inline-size,
+  // so we work in the parent's writing mode; but if aFrame is orthogonal to
+  // its parent, we'll need to look at its BSize instead of min/pref-ISize.
+  const nsStylePosition* stylePos = aFrame->StylePosition();
+  StyleBoxSizing boxSizing = stylePos->mBoxSizing;
+
+  const nsStyleCoord& styleMinISize =
+    horizontalAxis ? stylePos->mMinWidth : stylePos->mMinHeight;
+  const nsStyleCoord& styleISize =
+    (aFlags & MIN_INTRINSIC_ISIZE) ? styleMinISize :
+    (horizontalAxis ? stylePos->mWidth : stylePos->mHeight);
+  MOZ_ASSERT(!(aFlags & MIN_INTRINSIC_ISIZE) ||
+             styleISize.GetUnit() == eStyleUnit_Auto ||
+             styleISize.GetUnit() == eStyleUnit_Enumerated,
+             "should only use MIN_INTRINSIC_ISIZE for intrinsic values");
+  const nsStyleCoord& styleMaxISize =
+    horizontalAxis ? stylePos->mMaxWidth : stylePos->mMaxHeight;
+
+  // We build up two values starting with the content box, and then
+  // adding padding, border and margin.  The result is normally
+  // |result|.  Then, when we handle 'width', 'min-width', and
+  // 'max-width', we use the results we've been building in |min| as a
+  // minimum, overriding 'min-width'.  This ensures two things:
+  //   * that we don't let a value of 'box-sizing' specifying a width
+  //     smaller than the padding/border inside the box-sizing box give
+  //     a content width less than zero
+  //   * that we prevent tables from becoming smaller than their
+  //     intrinsic minimum width
+  nscoord result = 0, min = 0;
+
+  nscoord maxISize;
+  bool haveFixedMaxISize = GetAbsoluteCoord(styleMaxISize, maxISize);
+  nscoord minISize;
+
+  // Treat "min-width: auto" as 0.
+  bool haveFixedMinISize;
+  if (eStyleUnit_Auto == styleMinISize.GetUnit()) {
+    // NOTE: Technically, "auto" is supposed to behave like "min-content" on
+    // flex items. However, we don't need to worry about that here, because
+    // flex items' min-sizes are intentionally ignored until the flex
+    // container explicitly considers them during space distribution.
+    minISize = 0;
+    haveFixedMinISize = true;
+  } else {
+    haveFixedMinISize = GetAbsoluteCoord(styleMinISize, minISize);
+  }
+
+  PhysicalAxis ourInlineAxis =
+    aFrame->GetWritingMode().PhysicalAxis(eLogicalAxisInline);
+  // If we have a specified width (or a specified 'min-width' greater
+  // than the specified 'max-width', which works out to the same thing),
+  // don't even bother getting the frame's intrinsic width, because in
+  // this case GetAbsoluteCoord(styleISize, w) will always succeed, so
+  // we'll never need the intrinsic dimensions.
+  if (styleISize.GetUnit() == eStyleUnit_Enumerated &&
+      (styleISize.GetIntValue() == NS_STYLE_WIDTH_MAX_CONTENT ||
+       styleISize.GetIntValue() == NS_STYLE_WIDTH_MIN_CONTENT)) {
+    // -moz-fit-content and -moz-available enumerated widths compute intrinsic
+    // widths just like auto.
+    // For -moz-max-content and -moz-min-content, we handle them like
+    // specified widths, but ignore box-sizing.
+    boxSizing = StyleBoxSizing::Content;
+    if (aMarginBoxMinSizeClamp != NS_MAXSIZE &&
+        styleISize.GetIntValue() == NS_STYLE_WIDTH_MIN_CONTENT) {
+      // We need |result| to be the 'min-content size' for the clamping below.
+      result = aFrame->GetMinISize(aRenderingContext);
+    }
+  } else if (!styleISize.ConvertsToLength() &&
+             !(haveFixedMinISize && haveFixedMaxISize && maxISize <= minISize)) {
+#ifdef DEBUG_INTRINSIC_WIDTH
+    ++gNoiseIndent;
+#endif
+    if (aType != MIN_ISIZE) {
+      // At this point, |styleISize| is auto/-moz-fit-content/-moz-available or
+      // has a percentage.  The intrinisic size for those under a max-content
+      // constraint is the max-content contribution which we shouldn't clamp.
+      aMarginBoxMinSizeClamp = NS_MAXSIZE;
+    }
+    if (MOZ_UNLIKELY(aAxis != ourInlineAxis)) {
+      IntrinsicSize intrinsicSize = aFrame->GetIntrinsicSize();
+      const nsStyleCoord intrinsicBCoord =
+        horizontalAxis ? intrinsicSize.width : intrinsicSize.height;
+      if (intrinsicBCoord.GetUnit() == eStyleUnit_Coord) {
+        result = intrinsicBCoord.GetCoordValue();
+      } else {
+        // We don't have an intrinsic bsize and we need aFrame's block-dir size.
+        if (aFlags & BAIL_IF_REFLOW_NEEDED) {
+          return NS_INTRINSIC_WIDTH_UNKNOWN;
+        }
+        // XXX Unfortunately, we probably don't know this yet, so this is wrong...
+        // but it's not clear what we should do. If aFrame's inline size hasn't
+        // been determined yet, we can't necessarily figure out its block size
+        // either. For now, authors who put orthogonal elements into things like
+        // buttons or table cells may have to explicitly provide sizes rather
+        // than expecting intrinsic sizing to work "perfectly" in underspecified
+        // cases.
+        result = aFrame->BSize();
+      }
+    } else {
+      result = aType == MIN_ISIZE
+               ? aFrame->GetMinISize(aRenderingContext)
+               : aFrame->GetPrefISize(aRenderingContext);
+    }
+#ifdef DEBUG_INTRINSIC_WIDTH
+    --gNoiseIndent;
+    nsFrame::IndentBy(stderr, gNoiseIndent);
+    static_cast<nsFrame*>(aFrame)->ListTag(stderr);
+    printf_stderr(" %s %s intrinsic size from frame is %d.\n",
+                  aType == MIN_ISIZE ? "min" : "pref",
+                  horizontalAxis ? "horizontal" : "vertical",
+                  result);
+#endif
+
+    // Handle elements with an intrinsic ratio (or size) and a specified
+    // height, min-height, or max-height.
+    // NOTE: We treat "min-height:auto" as "0" for the purpose of this code,
+    // since that's what it means in all cases except for on flex items -- and
+    // even there, we're supposed to ignore it (i.e. treat it as 0) until the
+    // flex container explicitly considers it.
+    const nsStyleCoord& styleBSize =
+      horizontalAxis ? stylePos->mHeight : stylePos->mWidth;
+    const nsStyleCoord& styleMinBSize =
+      horizontalAxis ? stylePos->mMinHeight : stylePos->mMinWidth;
+    const nsStyleCoord& styleMaxBSize =
+      horizontalAxis ? stylePos->mMaxHeight : stylePos->mMaxWidth;
+
+    if (styleBSize.GetUnit() != eStyleUnit_Auto ||
+        !(styleMinBSize.GetUnit() == eStyleUnit_Auto ||
+          (styleMinBSize.GetUnit() == eStyleUnit_Coord &&
+           styleMinBSize.GetCoordValue() == 0)) ||
+        styleMaxBSize.GetUnit() != eStyleUnit_None) {
+
+      nsSize ratio(aFrame->GetIntrinsicRatio());
+      nscoord ratioISize = (horizontalAxis ? ratio.width  : ratio.height);
+      nscoord ratioBSize = (horizontalAxis ? ratio.height : ratio.width);
+      if (ratioBSize != 0) {
+        AddStateBitToAncestors(aFrame,
+            NS_FRAME_DESCENDANT_INTRINSIC_ISIZE_DEPENDS_ON_BSIZE);
+
+        nscoord bSizeTakenByBoxSizing =
+          GetBSizeTakenByBoxSizing(boxSizing, aFrame, horizontalAxis,
+                                   aFlags & IGNORE_PADDING);
+
+        // NOTE: This is only the minContentSize if we've been passed MIN_INTRINSIC_ISIZE
+        // (which is fine, because this should only be used inside a check for that flag).
+        nscoord minContentSize = result;
+        nscoord h;
+        if (GetAbsoluteCoord(styleBSize, h) ||
+            GetPercentBSize(styleBSize, aFrame, horizontalAxis, h)) {
+          h = std::max(0, h - bSizeTakenByBoxSizing);
+          result = NSCoordMulDiv(h, ratioISize, ratioBSize);
+        }
+
+        if (GetAbsoluteCoord(styleMaxBSize, h) ||
+            GetPercentBSize(styleMaxBSize, aFrame, horizontalAxis, h)) {
+          h = std::max(0, h - bSizeTakenByBoxSizing);
+          nscoord maxISize = NSCoordMulDiv(h, ratioISize, ratioBSize);
+          if (maxISize < result) {
+            result = maxISize;
+          }
+          if (maxISize < minContentSize) {
+            minContentSize = maxISize;
+          }
+        }
+
+        if (GetAbsoluteCoord(styleMinBSize, h) ||
+            GetPercentBSize(styleMinBSize, aFrame, horizontalAxis, h)) {
+          h = std::max(0, h - bSizeTakenByBoxSizing);
+          nscoord minISize = NSCoordMulDiv(h, ratioISize, ratioBSize);
+          if (minISize > result) {
+            result = minISize;
+          }
+          if (minISize > minContentSize) {
+            minContentSize = minISize;
+          }
+        }
+        if (MOZ_UNLIKELY(aFlags & nsLayoutUtils::MIN_INTRINSIC_ISIZE)) {
+          // This is the 'min-width/height:auto' "transferred size" piece of:
+          // https://www.w3.org/TR/css-flexbox-1/#min-width-automatic-minimum-size
+          // https://drafts.csswg.org/css-grid/#min-size-auto
+          result = std::min(result, minContentSize);
+        }
+      }
+    }
+  }
+
+  if (aFrame->GetType() == nsGkAtoms::tableFrame) {
+    // Tables can't shrink smaller than their intrinsic minimum width,
+    // no matter what.
+    min = aFrame->GetMinISize(aRenderingContext);
+  }
+
+  nsIFrame::IntrinsicISizeOffsetData offsets =
+    MOZ_LIKELY(aAxis == ourInlineAxis) ? aFrame->IntrinsicISizeOffsets()
+                                       : aFrame->IntrinsicBSizeOffsets();
+  nscoord contentBoxSize = result;
+  result = AddIntrinsicSizeOffset(aRenderingContext, aFrame, offsets, aType,
+                                  boxSizing, result, min, styleISize,
+                                  haveFixedMinISize ? &minISize : nullptr,
+                                  styleMinISize,
+                                  haveFixedMaxISize ? &maxISize : nullptr,
+                                  styleMaxISize,
+                                  aFlags, aAxis);
+  nscoord overflow = result - aMarginBoxMinSizeClamp;
+  if (MOZ_UNLIKELY(overflow > 0)) {
+    nscoord newContentBoxSize = std::max(nscoord(0), contentBoxSize - overflow);
+    result -= contentBoxSize - newContentBoxSize;
+  }
+
+#ifdef DEBUG_INTRINSIC_WIDTH
+  nsFrame::IndentBy(stderr, gNoiseIndent);
+  static_cast<nsFrame*>(aFrame)->ListTag(stderr);
+  printf_stderr(" %s %s intrinsic size for container is %d twips.\n",
+                aType == MIN_ISIZE ? "min" : "pref",
+                horizontalAxis ? "horizontal" : "vertical",
+                result);
+#endif
+
+  return result;
+}
+
+/* static */ nscoord
+nsLayoutUtils::IntrinsicForContainer(nsRenderingContext* aRenderingContext,
+                                     nsIFrame* aFrame,
+                                     IntrinsicISizeType aType,
+                                     uint32_t aFlags)
+{
+  MOZ_ASSERT(aFrame && aFrame->GetParent());
+  // We want the size aFrame will contribute to its parent's inline-size.
+  PhysicalAxis axis =
+    aFrame->GetParent()->GetWritingMode().PhysicalAxis(eLogicalAxisInline);
+  return IntrinsicForAxis(axis, aRenderingContext, aFrame, aType, aFlags);
+}
+
+/* static */ nscoord
+nsLayoutUtils::MinSizeContributionForAxis(PhysicalAxis        aAxis,
+                                          nsRenderingContext* aRC,
+                                          nsIFrame*           aFrame,
+                                          IntrinsicISizeType  aType,
+                                          uint32_t            aFlags)
+{
+  MOZ_ASSERT(aFrame);
+  MOZ_ASSERT(aFrame->IsFlexOrGridItem(),
+             "only grid/flex items have this behavior currently");
+
+#ifdef DEBUG_INTRINSIC_WIDTH
+  nsFrame::IndentBy(stderr, gNoiseIndent);
+  static_cast<nsFrame*>(aFrame)->ListTag(stderr);
+  printf_stderr(" %s min-isize for %s WM:\n",
+                aType == MIN_ISIZE ? "min" : "pref",
+                aWM.IsVertical() ? "vertical" : "horizontal");
+#endif
+
+  // Note: this method is only meant for grid/flex items which always
+  // include percentages in their intrinsic size.
+  aFlags |= nsLayoutUtils::ADD_PERCENTS;
+  const nsStylePosition* const stylePos = aFrame->StylePosition();
+  const nsStyleCoord* style = aAxis == eAxisHorizontal ? &stylePos->mMinWidth
+                                                       : &stylePos->mMinHeight;
+  nscoord minSize;
+  nscoord* fixedMinSize = nullptr;
+  auto minSizeUnit = style->GetUnit();
+  if (minSizeUnit == eStyleUnit_Auto) {
+    if (aFrame->StyleDisplay()->mOverflowX == NS_STYLE_OVERFLOW_VISIBLE) {
+      style = aAxis == eAxisHorizontal ? &stylePos->mWidth
+                                       : &stylePos->mHeight;
+      if (GetAbsoluteCoord(*style, minSize)) {
+        // We have a definite width/height.  This is the "specified size" in:
+        // https://drafts.csswg.org/css-grid/#min-size-auto
+        fixedMinSize = &minSize;
+      }
+      // fall through - the caller will have to deal with "transferred size"
+    } else {
+      // min-[width|height]:auto with overflow != visible computes to zero.
+      minSize = 0;
+      fixedMinSize = &minSize;
+    }
+  } else if (GetAbsoluteCoord(*style, minSize)) {
+    fixedMinSize = &minSize;
+  } else if (minSizeUnit != eStyleUnit_Enumerated) {
+    MOZ_ASSERT(style->HasPercent());
+    minSize = 0;
+    fixedMinSize = &minSize;
+  }
+
+  if (!fixedMinSize) {
+    // Let the caller deal with the "content size" cases.
+#ifdef DEBUG_INTRINSIC_WIDTH
+    nsFrame::IndentBy(stderr, gNoiseIndent);
+    static_cast<nsFrame*>(aFrame)->ListTag(stderr);
+    printf_stderr(" %s min-isize is indefinite.\n",
+                  aType == MIN_ISIZE ? "min" : "pref");
+#endif
+    return NS_UNCONSTRAINEDSIZE;
+  }
+
+  // If aFrame is a container for font size inflation, then shrink
+  // wrapping inside of it should not apply font size inflation.
+  AutoMaybeDisableFontInflation an(aFrame);
+
+  PhysicalAxis ourInlineAxis =
+    aFrame->GetWritingMode().PhysicalAxis(eLogicalAxisInline);
+  nsIFrame::IntrinsicISizeOffsetData offsets =
+    ourInlineAxis == aAxis ? aFrame->IntrinsicISizeOffsets()
+                           : aFrame->IntrinsicBSizeOffsets();
+  nscoord result = 0;
+  nscoord min = 0;
+
+  const nsStyleCoord& maxISize =
+    aAxis == eAxisHorizontal ? stylePos->mMaxWidth : stylePos->mMaxHeight;
+  result = AddIntrinsicSizeOffset(aRC, aFrame, offsets, aType,
+                                  stylePos->mBoxSizing,
+                                  result, min, *style, fixedMinSize,
+                                  *style, nullptr, maxISize, aFlags, aAxis);
+
+#ifdef DEBUG_INTRINSIC_WIDTH
+  nsFrame::IndentBy(stderr, gNoiseIndent);
+  static_cast<nsFrame*>(aFrame)->ListTag(stderr);
+  printf_stderr(" %s min-isize is %d twips.\n",
+         aType == MIN_ISIZE ? "min" : "pref", result);
+#endif
+
+  return result;
+}
+
+/* static */ nscoord
+nsLayoutUtils::ComputeCBDependentValue(nscoord aPercentBasis,
+                                       const nsStyleCoord& aCoord)
+{
+  NS_WARNING_ASSERTION(
+    aPercentBasis != NS_UNCONSTRAINEDSIZE,
+    "have unconstrained width or height; this should only result from very "
+    "large sizes, not attempts at intrinsic size calculation");
+
+  if (aCoord.IsCoordPercentCalcUnit()) {
+    return nsRuleNode::ComputeCoordPercentCalc(aCoord, aPercentBasis);
+  }
+  NS_ASSERTION(aCoord.GetUnit() == eStyleUnit_None ||
+               aCoord.GetUnit() == eStyleUnit_Auto,
+               "unexpected width value");
+  return 0;
+}
+
+/* static */ nscoord
+nsLayoutUtils::ComputeBSizeDependentValue(
+                 nscoord              aContainingBlockBSize,
+                 const nsStyleCoord&  aCoord)
+{
+  // XXXldb Some callers explicitly check aContainingBlockBSize
+  // against NS_AUTOHEIGHT *and* unit against eStyleUnit_Percent or
+  // calc()s containing percents before calling this function.
+  // However, it would be much more likely to catch problems without
+  // the unit conditions.
+  // XXXldb Many callers pass a non-'auto' containing block height when
+  // according to CSS2.1 they should be passing 'auto'.
+  NS_PRECONDITION(NS_AUTOHEIGHT != aContainingBlockBSize ||
+                  !aCoord.HasPercent(),
+                  "unexpected containing block block-size");
+
+  if (aCoord.IsCoordPercentCalcUnit()) {
+    return nsRuleNode::ComputeCoordPercentCalc(aCoord, aContainingBlockBSize);
+  }
+
+  NS_ASSERTION(aCoord.GetUnit() == eStyleUnit_None ||
+               aCoord.GetUnit() == eStyleUnit_Auto,
+               "unexpected block-size value");
+  return 0;
+}
+
+/* static */ void
+nsLayoutUtils::MarkDescendantsDirty(nsIFrame *aSubtreeRoot)
+{
+  AutoTArray<nsIFrame*, 4> subtrees;
+  subtrees.AppendElement(aSubtreeRoot);
+
+  // dirty descendants, iterating over subtrees that may include
+  // additional subtrees associated with placeholders
+  do {
+    nsIFrame *subtreeRoot = subtrees.ElementAt(subtrees.Length() - 1);
+    subtrees.RemoveElementAt(subtrees.Length() - 1);
+
+    // Mark all descendants dirty (using an nsTArray stack rather than
+    // recursion).
+    // Note that ReflowInput::InitResizeFlags has some similar
+    // code; see comments there for how and why it differs.
+    AutoTArray<nsIFrame*, 32> stack;
+    stack.AppendElement(subtreeRoot);
+
+    do {
+      nsIFrame *f = stack.ElementAt(stack.Length() - 1);
+      stack.RemoveElementAt(stack.Length() - 1);
+
+      f->MarkIntrinsicISizesDirty();
+
+      if (f->GetType() == nsGkAtoms::placeholderFrame) {
+        nsIFrame *oof = nsPlaceholderFrame::GetRealFrameForPlaceholder(f);
+        if (!nsLayoutUtils::IsProperAncestorFrame(subtreeRoot, oof)) {
+          // We have another distinct subtree we need to mark.
+          subtrees.AppendElement(oof);
+        }
+      }
+
+      nsIFrame::ChildListIterator lists(f);
+      for (; !lists.IsDone(); lists.Next()) {
+        nsFrameList::Enumerator childFrames(lists.CurrentList());
+        for (; !childFrames.AtEnd(); childFrames.Next()) {
+          nsIFrame* kid = childFrames.get();
+          stack.AppendElement(kid);
+        }
+      }
+    } while (stack.Length() != 0);
+  } while (subtrees.Length() != 0);
+}
+
+/* static */
+void
+nsLayoutUtils::MarkIntrinsicISizesDirtyIfDependentOnBSize(nsIFrame* aFrame)
+{
+  AutoTArray<nsIFrame*, 32> stack;
+  stack.AppendElement(aFrame);
+
+  do {
+    nsIFrame* f = stack.ElementAt(stack.Length() - 1);
+    stack.RemoveElementAt(stack.Length() - 1);
+
+    if (!f->HasAnyStateBits(
+        NS_FRAME_DESCENDANT_INTRINSIC_ISIZE_DEPENDS_ON_BSIZE)) {
+      continue;
+    }
+    f->MarkIntrinsicISizesDirty();
+
+    for (nsIFrame::ChildListIterator lists(f); !lists.IsDone(); lists.Next()) {
+      for (nsIFrame* kid : lists.CurrentList()) {
+        stack.AppendElement(kid);
+      }
+    }
+  } while (stack.Length() != 0);
+}
+
+nsSize
+nsLayoutUtils::ComputeAutoSizeWithIntrinsicDimensions(nscoord minWidth, nscoord minHeight,
+                                                      nscoord maxWidth, nscoord maxHeight,
+                                                      nscoord tentWidth, nscoord tentHeight)
+{
+  // Now apply min/max-width/height - CSS 2.1 sections 10.4 and 10.7:
+
+  if (minWidth > maxWidth)
+    maxWidth = minWidth;
+  if (minHeight > maxHeight)
+    maxHeight = minHeight;
+
+  nscoord heightAtMaxWidth, heightAtMinWidth,
+          widthAtMaxHeight, widthAtMinHeight;
+
+  if (tentWidth > 0) {
+    heightAtMaxWidth = NSCoordMulDiv(maxWidth, tentHeight, tentWidth);
+    if (heightAtMaxWidth < minHeight)
+      heightAtMaxWidth = minHeight;
+    heightAtMinWidth = NSCoordMulDiv(minWidth, tentHeight, tentWidth);
+    if (heightAtMinWidth > maxHeight)
+      heightAtMinWidth = maxHeight;
+  } else {
+    heightAtMaxWidth = heightAtMinWidth = NS_CSS_MINMAX(tentHeight, minHeight, maxHeight);
+  }
+
+  if (tentHeight > 0) {
+    widthAtMaxHeight = NSCoordMulDiv(maxHeight, tentWidth, tentHeight);
+    if (widthAtMaxHeight < minWidth)
+      widthAtMaxHeight = minWidth;
+    widthAtMinHeight = NSCoordMulDiv(minHeight, tentWidth, tentHeight);
+    if (widthAtMinHeight > maxWidth)
+      widthAtMinHeight = maxWidth;
+  } else {
+    widthAtMaxHeight = widthAtMinHeight = NS_CSS_MINMAX(tentWidth, minWidth, maxWidth);
+  }
+
+  // The table at http://www.w3.org/TR/CSS21/visudet.html#min-max-widths :
+
+  nscoord width, height;
+
+  if (tentWidth > maxWidth) {
+    if (tentHeight > maxHeight) {
+      if (int64_t(maxWidth) * int64_t(tentHeight) <=
+          int64_t(maxHeight) * int64_t(tentWidth)) {
+        width = maxWidth;
+        height = heightAtMaxWidth;
+      } else {
+        width = widthAtMaxHeight;
+        height = maxHeight;
+      }
+    } else {
+      // This also covers "(w > max-width) and (h < min-height)" since in
+      // that case (max-width/w < 1), and with (h < min-height):
+      //   max(max-width * h/w, min-height) == min-height
+      width = maxWidth;
+      height = heightAtMaxWidth;
+    }
+  } else if (tentWidth < minWidth) {
+    if (tentHeight < minHeight) {
+      if (int64_t(minWidth) * int64_t(tentHeight) <=
+          int64_t(minHeight) * int64_t(tentWidth)) {
+        width = widthAtMinHeight;
+        height = minHeight;
+      } else {
+        width = minWidth;
+        height = heightAtMinWidth;
+      }
+    } else {
+      // This also covers "(w < min-width) and (h > max-height)" since in
+      // that case (min-width/w > 1), and with (h > max-height):
+      //   min(min-width * h/w, max-height) == max-height
+      width = minWidth;
+      height = heightAtMinWidth;
+    }
+  } else {
+    if (tentHeight > maxHeight) {
+      width = widthAtMaxHeight;
+      height = maxHeight;
+    } else if (tentHeight < minHeight) {
+      width = widthAtMinHeight;
+      height = minHeight;
+    } else {
+      width = tentWidth;
+      height = tentHeight;
+    }
+  }
+
+  return nsSize(width, height);
+}
+
+/* static */ nscoord
+nsLayoutUtils::MinISizeFromInline(nsIFrame* aFrame,
+                                  nsRenderingContext* aRenderingContext)
+{
+  NS_ASSERTION(!aFrame->IsContainerForFontSizeInflation(),
+               "should not be container for font size inflation");
+
+  nsIFrame::InlineMinISizeData data;
+  DISPLAY_MIN_WIDTH(aFrame, data.mPrevLines);
+  aFrame->AddInlineMinISize(aRenderingContext, &data);
+  data.ForceBreak();
+  return data.mPrevLines;
+}
+
+/* static */ nscoord
+nsLayoutUtils::PrefISizeFromInline(nsIFrame* aFrame,
+                                   nsRenderingContext* aRenderingContext)
+{
+  NS_ASSERTION(!aFrame->IsContainerForFontSizeInflation(),
+               "should not be container for font size inflation");
+
+  nsIFrame::InlinePrefISizeData data;
+  DISPLAY_PREF_WIDTH(aFrame, data.mPrevLines);
+  aFrame->AddInlinePrefISize(aRenderingContext, &data);
+  data.ForceBreak();
+  return data.mPrevLines;
+}
+
+static nscolor
+DarkenColor(nscolor aColor)
+{
+  uint16_t  hue, sat, value;
+  uint8_t alpha;
+
+  // convert the RBG to HSV so we can get the lightness (which is the v)
+  NS_RGB2HSV(aColor, hue, sat, value, alpha);
+
+  // The goal here is to send white to black while letting colored
+  // stuff stay colored... So we adopt the following approach.
+  // Something with sat = 0 should end up with value = 0.  Something
+  // with a high sat can end up with a high value and it's ok.... At
+  // the same time, we don't want to make things lighter.  Do
+  // something simple, since it seems to work.
+  if (value > sat) {
+    value = sat;
+    // convert this color back into the RGB color space.
+    NS_HSV2RGB(aColor, hue, sat, value, alpha);
+  }
+  return aColor;
+}
+
+// Check whether we should darken text/decoration colors. We need to do this if
+// background images and colors are being suppressed, because that means
+// light text will not be visible against the (presumed light-colored) background.
+static bool
+ShouldDarkenColors(nsPresContext* aPresContext)
+{
+  return !aPresContext->GetBackgroundColorDraw() &&
+         !aPresContext->GetBackgroundImageDraw();
+}
+
+nscolor
+nsLayoutUtils::GetColor(nsIFrame* aFrame, nsCSSPropertyID aProperty)
+{
+  nscolor color = aFrame->GetVisitedDependentColor(aProperty);
+  if (ShouldDarkenColors(aFrame->PresContext())) {
+    color = DarkenColor(color);
+  }
+  return color;
+}
+
+gfxFloat
+nsLayoutUtils::GetSnappedBaselineY(nsIFrame* aFrame, gfxContext* aContext,
+                                   nscoord aY, nscoord aAscent)
+{
+  gfxFloat appUnitsPerDevUnit = aFrame->PresContext()->AppUnitsPerDevPixel();
+  gfxFloat baseline = gfxFloat(aY) + aAscent;
+  gfxRect putativeRect(0, baseline/appUnitsPerDevUnit, 1, 1);
+  if (!aContext->UserToDevicePixelSnapped(putativeRect, true))
+    return baseline;
+  return aContext->DeviceToUser(putativeRect.TopLeft()).y * appUnitsPerDevUnit;
+}
+
+gfxFloat
+nsLayoutUtils::GetSnappedBaselineX(nsIFrame* aFrame, gfxContext* aContext,
+                                   nscoord aX, nscoord aAscent)
+{
+  gfxFloat appUnitsPerDevUnit = aFrame->PresContext()->AppUnitsPerDevPixel();
+  gfxFloat baseline = gfxFloat(aX) + aAscent;
+  gfxRect putativeRect(baseline / appUnitsPerDevUnit, 0, 1, 1);
+  if (!aContext->UserToDevicePixelSnapped(putativeRect, true)) {
+    return baseline;
+  }
+  return aContext->DeviceToUser(putativeRect.TopLeft()).x * appUnitsPerDevUnit;
+}
+
+// Hard limit substring lengths to 8000 characters ... this lets us statically
+// size the cluster buffer array in FindSafeLength
+#define MAX_GFX_TEXT_BUF_SIZE 8000
+
+static int32_t FindSafeLength(const char16_t *aString, uint32_t aLength,
+                              uint32_t aMaxChunkLength)
+{
+  if (aLength <= aMaxChunkLength)
+    return aLength;
+
+  int32_t len = aMaxChunkLength;
+
+  // Ensure that we don't break inside a surrogate pair
+  while (len > 0 && NS_IS_LOW_SURROGATE(aString[len])) {
+    len--;
+  }
+  if (len == 0) {
+    // We don't want our caller to go into an infinite loop, so don't
+    // return zero. It's hard to imagine how we could actually get here
+    // unless there are languages that allow clusters of arbitrary size.
+    // If there are and someone feeds us a 500+ character cluster, too
+    // bad.
+    return aMaxChunkLength;
+  }
+  return len;
+}
+
+static int32_t GetMaxChunkLength(nsFontMetrics& aFontMetrics)
+{
+  return std::min(aFontMetrics.GetMaxStringLength(), MAX_GFX_TEXT_BUF_SIZE);
+}
+
+nscoord
+nsLayoutUtils::AppUnitWidthOfString(const char16_t *aString,
+                                    uint32_t aLength,
+                                    nsFontMetrics& aFontMetrics,
+                                    DrawTarget* aDrawTarget)
+{
+  uint32_t maxChunkLength = GetMaxChunkLength(aFontMetrics);
+  nscoord width = 0;
+  while (aLength > 0) {
+    int32_t len = FindSafeLength(aString, aLength, maxChunkLength);
+    width += aFontMetrics.GetWidth(aString, len, aDrawTarget);
+    aLength -= len;
+    aString += len;
+  }
+  return width;
+}
+
+nscoord
+nsLayoutUtils::AppUnitWidthOfStringBidi(const char16_t* aString,
+                                        uint32_t aLength,
+                                        const nsIFrame* aFrame,
+                                        nsFontMetrics& aFontMetrics,
+                                        nsRenderingContext& aContext)
+{
+  nsPresContext* presContext = aFrame->PresContext();
+  if (presContext->BidiEnabled()) {
+    nsBidiLevel level =
+      nsBidiPresUtils::BidiLevelFromStyle(aFrame->StyleContext());
+    return nsBidiPresUtils::MeasureTextWidth(aString, aLength, level,
+                                             presContext, aContext,
+                                             aFontMetrics);
+  }
+  aFontMetrics.SetTextRunRTL(false);
+  aFontMetrics.SetVertical(aFrame->GetWritingMode().IsVertical());
+  aFontMetrics.SetTextOrientation(aFrame->StyleVisibility()->mTextOrientation);
+  return nsLayoutUtils::AppUnitWidthOfString(aString, aLength, aFontMetrics,
+                                             aContext.GetDrawTarget());
+}
+
+bool
+nsLayoutUtils::StringWidthIsGreaterThan(const nsString& aString,
+                                        nsFontMetrics& aFontMetrics,
+                                        DrawTarget* aDrawTarget,
+                                        nscoord aWidth)
+{
+  const char16_t *string = aString.get();
+  uint32_t length = aString.Length();
+  uint32_t maxChunkLength = GetMaxChunkLength(aFontMetrics);
+  nscoord width = 0;
+  while (length > 0) {
+    int32_t len = FindSafeLength(string, length, maxChunkLength);
+    width += aFontMetrics.GetWidth(string, len, aDrawTarget);
+    if (width > aWidth) {
+      return true;
+    }
+    length -= len;
+    string += len;
+  }
+  return false;
+}
+
+nsBoundingMetrics
+nsLayoutUtils::AppUnitBoundsOfString(const char16_t* aString,
+                                     uint32_t aLength,
+                                     nsFontMetrics& aFontMetrics,
+                                     DrawTarget* aDrawTarget)
+{
+  uint32_t maxChunkLength = GetMaxChunkLength(aFontMetrics);
+  int32_t len = FindSafeLength(aString, aLength, maxChunkLength);
+  // Assign directly in the first iteration. This ensures that
+  // negative ascent/descent can be returned and the left bearing
+  // is properly initialized.
+  nsBoundingMetrics totalMetrics =
+    aFontMetrics.GetBoundingMetrics(aString, len, aDrawTarget);
+  aLength -= len;
+  aString += len;
+
+  while (aLength > 0) {
+    len = FindSafeLength(aString, aLength, maxChunkLength);
+    nsBoundingMetrics metrics =
+      aFontMetrics.GetBoundingMetrics(aString, len, aDrawTarget);
+    totalMetrics += metrics;
+    aLength -= len;
+    aString += len;
+  }
+  return totalMetrics;
+}
+
+void
+nsLayoutUtils::DrawString(const nsIFrame*       aFrame,
+                          nsFontMetrics&        aFontMetrics,
+                          nsRenderingContext*   aContext,
+                          const char16_t*      aString,
+                          int32_t               aLength,
+                          nsPoint               aPoint,
+                          nsStyleContext*       aStyleContext)
+{
+  nsresult rv = NS_ERROR_FAILURE;
+
+  // If caller didn't pass a style context, use the frame's.
+  if (!aStyleContext) {
+    aStyleContext = aFrame->StyleContext();
+  }
+  aFontMetrics.SetVertical(WritingMode(aStyleContext).IsVertical());
+  aFontMetrics.SetTextOrientation(
+    aStyleContext->StyleVisibility()->mTextOrientation);
+
+  nsPresContext* presContext = aFrame->PresContext();
+  if (presContext->BidiEnabled()) {
+    nsBidiLevel level =
+      nsBidiPresUtils::BidiLevelFromStyle(aStyleContext);
+    rv = nsBidiPresUtils::RenderText(aString, aLength, level,
+                                     presContext, *aContext,
+                                     aContext->GetDrawTarget(), aFontMetrics,
+                                     aPoint.x, aPoint.y);
+  }
+  if (NS_FAILED(rv))
+  {
+    aFontMetrics.SetTextRunRTL(false);
+    DrawUniDirString(aString, aLength, aPoint, aFontMetrics, *aContext);
+  }
+}
+
+void
+nsLayoutUtils::DrawUniDirString(const char16_t* aString,
+                                uint32_t aLength,
+                                nsPoint aPoint,
+                                nsFontMetrics& aFontMetrics,
+                                nsRenderingContext& aContext)
+{
+  nscoord x = aPoint.x;
+  nscoord y = aPoint.y;
+
+  uint32_t maxChunkLength = GetMaxChunkLength(aFontMetrics);
+  if (aLength <= maxChunkLength) {
+    aFontMetrics.DrawString(aString, aLength, x, y, &aContext,
+                            aContext.GetDrawTarget());
+    return;
+  }
+
+  bool isRTL = aFontMetrics.GetTextRunRTL();
+
+  // If we're drawing right to left, we must start at the end.
+  if (isRTL) {
+    x += nsLayoutUtils::AppUnitWidthOfString(aString, aLength, aFontMetrics,
+                                             aContext.GetDrawTarget());
+  }
+
+  while (aLength > 0) {
+    int32_t len = FindSafeLength(aString, aLength, maxChunkLength);
+    nscoord width = aFontMetrics.GetWidth(aString, len, aContext.GetDrawTarget());
+    if (isRTL) {
+      x -= width;
+    }
+    aFontMetrics.DrawString(aString, len, x, y, &aContext,
+                            aContext.GetDrawTarget());
+    if (!isRTL) {
+      x += width;
+    }
+    aLength -= len;
+    aString += len;
+  }
+}
+
+/* static */ void
+nsLayoutUtils::PaintTextShadow(const nsIFrame* aFrame,
+                               nsRenderingContext* aContext,
+                               const nsRect& aTextRect,
+                               const nsRect& aDirtyRect,
+                               const nscolor& aForegroundColor,
+                               TextShadowCallback aCallback,
+                               void* aCallbackData)
+{
+  const nsStyleText* textStyle = aFrame->StyleText();
+  if (!textStyle->HasTextShadow())
+    return;
+
+  // Text shadow happens with the last value being painted at the back,
+  // ie. it is painted first.
+  gfxContext* aDestCtx = aContext->ThebesContext();
+  for (uint32_t i = textStyle->mTextShadow->Length(); i > 0; --i) {
+    nsCSSShadowItem* shadowDetails = textStyle->mTextShadow->ShadowAt(i - 1);
+    nsPoint shadowOffset(shadowDetails->mXOffset,
+                         shadowDetails->mYOffset);
+    nscoord blurRadius = std::max(shadowDetails->mRadius, 0);
+
+    nsRect shadowRect(aTextRect);
+    shadowRect.MoveBy(shadowOffset);
+
+    nsPresContext* presCtx = aFrame->PresContext();
+    nsContextBoxBlur contextBoxBlur;
+    gfxContext* shadowContext = contextBoxBlur.Init(shadowRect, 0, blurRadius,
+                                                    presCtx->AppUnitsPerDevPixel(),
+                                                    aDestCtx, aDirtyRect, nullptr);
+    if (!shadowContext)
+      continue;
+
+    nscolor shadowColor;
+    if (shadowDetails->mHasColor)
+      shadowColor = shadowDetails->mColor;
+    else
+      shadowColor = aForegroundColor;
+
+    // Conjure an nsRenderingContext from a gfxContext for drawing the text
+    // to blur.
+    nsRenderingContext renderingContext(shadowContext);
+
+    aDestCtx->Save();
+    aDestCtx->NewPath();
+    aDestCtx->SetColor(Color::FromABGR(shadowColor));
+
+    // The callback will draw whatever we want to blur as a shadow.
+    aCallback(&renderingContext, shadowOffset, shadowColor, aCallbackData);
+
+    contextBoxBlur.DoPaint();
+    aDestCtx->Restore();
+  }
+}
+
+/* static */ nscoord
+nsLayoutUtils::GetCenteredFontBaseline(nsFontMetrics* aFontMetrics,
+                                       nscoord        aLineHeight,
+                                       bool           aIsInverted)
+{
+  nscoord fontAscent = aIsInverted ? aFontMetrics->MaxDescent()
+                                   : aFontMetrics->MaxAscent();
+  nscoord fontHeight = aFontMetrics->MaxHeight();
+
+  nscoord leading = aLineHeight - fontHeight;
+  return fontAscent + leading/2;
+}
+
+
+/* static */ bool
+nsLayoutUtils::GetFirstLineBaseline(WritingMode aWritingMode,
+                                    const nsIFrame* aFrame, nscoord* aResult)
+{
+  LinePosition position;
+  if (!GetFirstLinePosition(aWritingMode, aFrame, &position))
+    return false;
+  *aResult = position.mBaseline;
+  return true;
+}
+
+/* static */ bool
+nsLayoutUtils::GetFirstLinePosition(WritingMode aWM,
+                                    const nsIFrame* aFrame,
+                                    LinePosition* aResult)
+{
+  const nsBlockFrame* block = nsLayoutUtils::GetAsBlock(const_cast<nsIFrame*>(aFrame));
+  if (!block) {
+    // For the first-line baseline we also have to check for a table, and if
+    // so, use the baseline of its first row.
+    nsIAtom* fType = aFrame->GetType();
+    if (fType == nsGkAtoms::tableWrapperFrame  ||
+        fType == nsGkAtoms::flexContainerFrame ||
+        fType == nsGkAtoms::gridContainerFrame) {
+      if ((fType == nsGkAtoms::gridContainerFrame &&
+           aFrame->HasAnyStateBits(NS_STATE_GRID_SYNTHESIZE_BASELINE)) ||
+          (fType == nsGkAtoms::flexContainerFrame &&
+           aFrame->HasAnyStateBits(NS_STATE_FLEX_SYNTHESIZE_BASELINE)) ||
+          (fType == nsGkAtoms::tableWrapperFrame &&
+           static_cast<const nsTableWrapperFrame*>(aFrame)->GetRowCount() == 0)) {
+        // empty grid/flex/table container
+        aResult->mBStart = 0;
+        aResult->mBaseline = aFrame->SynthesizeBaselineBOffsetFromBorderBox(aWM,
+                                       BaselineSharingGroup::eFirst);
+        aResult->mBEnd = aFrame->BSize(aWM);
+        return true;
+      }
+      aResult->mBStart = 0;
+      aResult->mBaseline = aFrame->GetLogicalBaseline(aWM);
+      // This is what we want for the list bullet caller; not sure if
+      // other future callers will want the same.
+      aResult->mBEnd = aFrame->BSize(aWM);
+      return true;
+    }
+
+    // For first-line baselines, we have to consider scroll frames.
+    if (fType == nsGkAtoms::scrollFrame) {
+      nsIScrollableFrame *sFrame = do_QueryFrame(const_cast<nsIFrame*>(aFrame));
+      if (!sFrame) {
+        NS_NOTREACHED("not scroll frame");
+      }
+      LinePosition kidPosition;
+      if (GetFirstLinePosition(aWM,
+                               sFrame->GetScrolledFrame(), &kidPosition)) {
+        // Consider only the border and padding that contributes to the
+        // kid's position, not the scrolling, so we get the initial
+        // position.
+        *aResult = kidPosition +
+          aFrame->GetLogicalUsedBorderAndPadding(aWM).BStart(aWM);
+        return true;
+      }
+      return false;
+    }
+
+    if (fType == nsGkAtoms::fieldSetFrame) {
+      LinePosition kidPosition;
+      nsIFrame* kid = aFrame->PrincipalChildList().FirstChild();
+      // kid might be a legend frame here, but that's ok.
+      if (GetFirstLinePosition(aWM, kid, &kidPosition)) {
+        *aResult = kidPosition +
+          kid->GetLogicalNormalPosition(aWM, aFrame->GetSize()).B(aWM);
+        return true;
+      }
+      return false;
+    }
+
+    // No baseline.
+    return false;
+  }
+
+  for (nsBlockFrame::ConstLineIterator line = block->LinesBegin(),
+                                       line_end = block->LinesEnd();
+       line != line_end; ++line) {
+    if (line->IsBlock()) {
+      nsIFrame *kid = line->mFirstChild;
+      LinePosition kidPosition;
+      if (GetFirstLinePosition(aWM, kid, &kidPosition)) {
+        //XXX Not sure if this is the correct value to use for container
+        //    width here. It will only be used in vertical-rl layout,
+        //    which we don't have full support and testing for yet.
+        const nsSize& containerSize = line->mContainerSize;
+        *aResult = kidPosition +
+                   kid->GetLogicalNormalPosition(aWM, containerSize).B(aWM);
+        return true;
+      }
+    } else {
+      // XXX Is this the right test?  We have some bogus empty lines
+      // floating around, but IsEmpty is perhaps too weak.
+      if (line->BSize() != 0 || !line->IsEmpty()) {
+        nscoord bStart = line->BStart();
+        aResult->mBStart = bStart;
+        aResult->mBaseline = bStart + line->GetLogicalAscent();
+        aResult->mBEnd = bStart + line->BSize();
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+/* static */ bool
+nsLayoutUtils::GetLastLineBaseline(WritingMode aWM,
+                                   const nsIFrame* aFrame, nscoord* aResult)
+{
+  const nsBlockFrame* block = nsLayoutUtils::GetAsBlock(const_cast<nsIFrame*>(aFrame));
+  if (!block)
+    // No baseline.  (We intentionally don't descend into scroll frames.)
+    return false;
+
+  for (nsBlockFrame::ConstReverseLineIterator line = block->LinesRBegin(),
+                                              line_end = block->LinesREnd();
+       line != line_end; ++line) {
+    if (line->IsBlock()) {
+      nsIFrame *kid = line->mFirstChild;
+      nscoord kidBaseline;
+      const nsSize& containerSize = line->mContainerSize;
+      if (GetLastLineBaseline(aWM, kid, &kidBaseline)) {
+        // Ignore relative positioning for baseline calculations
+        *aResult = kidBaseline +
+          kid->GetLogicalNormalPosition(aWM, containerSize).B(aWM);
+        return true;
+      } else if (kid->GetType() == nsGkAtoms::scrollFrame) {
+        // Use the bottom of the scroll frame.
+        // XXX CSS2.1 really doesn't say what to do here.
+        *aResult = kid->GetLogicalNormalPosition(aWM, containerSize).B(aWM) +
+                   kid->BSize(aWM);
+        return true;
+      }
+    } else {
+      // XXX Is this the right test?  We have some bogus empty lines
+      // floating around, but IsEmpty is perhaps too weak.
+      if (line->BSize() != 0 || !line->IsEmpty()) {
+        *aResult = line->BStart() + line->GetLogicalAscent();
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+static nscoord
+CalculateBlockContentBEnd(WritingMode aWM, nsBlockFrame* aFrame)
+{
+  NS_PRECONDITION(aFrame, "null ptr");
+
+  nscoord contentBEnd = 0;
+
+  for (nsBlockFrame::LineIterator line = aFrame->LinesBegin(),
+                                  line_end = aFrame->LinesEnd();
+       line != line_end; ++line) {
+    if (line->IsBlock()) {
+      nsIFrame* child = line->mFirstChild;
+      const nsSize& containerSize = line->mContainerSize;
+      nscoord offset =
+        child->GetLogicalNormalPosition(aWM, containerSize).B(aWM);
+      contentBEnd =
+        std::max(contentBEnd,
+                 nsLayoutUtils::CalculateContentBEnd(aWM, child) + offset);
+    }
+    else {
+      contentBEnd = std::max(contentBEnd, line->BEnd());
+    }
+  }
+  return contentBEnd;
+}
+
+/* static */ nscoord
+nsLayoutUtils::CalculateContentBEnd(WritingMode aWM, nsIFrame* aFrame)
+{
+  NS_PRECONDITION(aFrame, "null ptr");
+
+  nscoord contentBEnd = aFrame->BSize(aWM);
+
+  // We want scrollable overflow rather than visual because this
+  // calculation is intended to affect layout.
+  LogicalSize overflowSize(aWM, aFrame->GetScrollableOverflowRect().Size());
+  if (overflowSize.BSize(aWM) > contentBEnd) {
+    nsIFrame::ChildListIDs skip(nsIFrame::kOverflowList |
+                                nsIFrame::kExcessOverflowContainersList |
+                                nsIFrame::kOverflowOutOfFlowList);
+    nsBlockFrame* blockFrame = GetAsBlock(aFrame);
+    if (blockFrame) {
+      contentBEnd =
+        std::max(contentBEnd, CalculateBlockContentBEnd(aWM, blockFrame));
+      skip |= nsIFrame::kPrincipalList;
+    }
+    nsIFrame::ChildListIterator lists(aFrame);
+    for (; !lists.IsDone(); lists.Next()) {
+      if (!skip.Contains(lists.CurrentID())) {
+        nsFrameList::Enumerator childFrames(lists.CurrentList());
+        for (; !childFrames.AtEnd(); childFrames.Next()) {
+          nsIFrame* child = childFrames.get();
+          nscoord offset =
+            child->GetLogicalNormalPosition(aWM,
+                                            aFrame->GetSize()).B(aWM);
+          contentBEnd = std::max(contentBEnd,
+                                 CalculateContentBEnd(aWM, child) + offset);
+        }
+      }
+    }
+  }
+  return contentBEnd;
+}
+
+/* static */ nsIFrame*
+nsLayoutUtils::GetClosestLayer(nsIFrame* aFrame)
+{
+  nsIFrame* layer;
+  for (layer = aFrame; layer; layer = layer->GetParent()) {
+    if (layer->IsAbsPosContainingBlock() ||
+        (layer->GetParent() &&
+          layer->GetParent()->GetType() == nsGkAtoms::scrollFrame))
+      break;
+  }
+  if (layer)
+    return layer;
+  return aFrame->PresContext()->PresShell()->FrameManager()->GetRootFrame();
+}
+
+SamplingFilter
+nsLayoutUtils::GetSamplingFilterForFrame(nsIFrame* aForFrame)
+{
+  SamplingFilter defaultFilter = SamplingFilter::GOOD;
+  nsStyleContext *sc;
+  if (nsCSSRendering::IsCanvasFrame(aForFrame)) {
+    nsCSSRendering::FindBackground(aForFrame, &sc);
+  } else {
+    sc = aForFrame->StyleContext();
+  }
+
+  switch (sc->StyleVisibility()->mImageRendering) {
+  case NS_STYLE_IMAGE_RENDERING_OPTIMIZESPEED:
+    return SamplingFilter::POINT;
+  case NS_STYLE_IMAGE_RENDERING_OPTIMIZEQUALITY:
+    return SamplingFilter::LINEAR;
+  case NS_STYLE_IMAGE_RENDERING_CRISPEDGES:
+    return SamplingFilter::POINT;
+  default:
+    return defaultFilter;
+  }
+}
+
+/**
+ * Given an image being drawn into an appunit coordinate system, and
+ * a point in that coordinate system, map the point back into image
+ * pixel space.
+ * @param aSize the size of the image, in pixels
+ * @param aDest the rectangle that the image is being mapped into
+ * @param aPt a point in the same coordinate system as the rectangle
+ */
+static gfxPoint
+MapToFloatImagePixels(const gfxSize& aSize,
+                      const gfxRect& aDest, const gfxPoint& aPt)
+{
+  return gfxPoint(((aPt.x - aDest.X())*aSize.width)/aDest.Width(),
+                  ((aPt.y - aDest.Y())*aSize.height)/aDest.Height());
+}
+
+/**
+ * Given an image being drawn into an pixel-based coordinate system, and
+ * a point in image space, map the point into the pixel-based coordinate
+ * system.
+ * @param aSize the size of the image, in pixels
+ * @param aDest the rectangle that the image is being mapped into
+ * @param aPt a point in image space
+ */
+static gfxPoint
+MapToFloatUserPixels(const gfxSize& aSize,
+                     const gfxRect& aDest, const gfxPoint& aPt)
+{
+  return gfxPoint(aPt.x*aDest.Width()/aSize.width + aDest.X(),
+                  aPt.y*aDest.Height()/aSize.height + aDest.Y());
+}
+
+/* static */ gfxRect
+nsLayoutUtils::RectToGfxRect(const nsRect& aRect, int32_t aAppUnitsPerDevPixel)
+{
+  return gfxRect(gfxFloat(aRect.x) / aAppUnitsPerDevPixel,
+                 gfxFloat(aRect.y) / aAppUnitsPerDevPixel,
+                 gfxFloat(aRect.width) / aAppUnitsPerDevPixel,
+                 gfxFloat(aRect.height) / aAppUnitsPerDevPixel);
+}
+
+struct SnappedImageDrawingParameters {
+  // A transform from image space to device space.
+  gfxMatrix imageSpaceToDeviceSpace;
+  // The size at which the image should be drawn (which may not be its
+  // intrinsic size due to, for example, HQ scaling).
+  nsIntSize size;
+  // The region in tiled image space which will be drawn, with an associated
+  // region to which sampling should be restricted.
+  ImageRegion region;
+  // The default viewport size for SVG images, which we use unless a different
+  // one has been explicitly specified. This is the same as |size| except that
+  // it does not take into account any transformation on the gfxContext we're
+  // drawing to - for example, CSS transforms are not taken into account.
+  CSSIntSize svgViewportSize;
+  // Whether there's anything to draw at all.
+  bool shouldDraw;
+
+  SnappedImageDrawingParameters()
+   : region(ImageRegion::Empty())
+   , shouldDraw(false)
+  {}
+
+  SnappedImageDrawingParameters(const gfxMatrix&   aImageSpaceToDeviceSpace,
+                                const nsIntSize&   aSize,
+                                const ImageRegion& aRegion,
+                                const CSSIntSize&  aSVGViewportSize)
+   : imageSpaceToDeviceSpace(aImageSpaceToDeviceSpace)
+   , size(aSize)
+   , region(aRegion)
+   , svgViewportSize(aSVGViewportSize)
+   , shouldDraw(true)
+  {}
+};
+
+/**
+ * Given two axis-aligned rectangles, returns the transformation that maps the
+ * first onto the second.
+ *
+ * @param aFrom The rect to be transformed.
+ * @param aTo The rect that aFrom should be mapped onto by the transformation.
+ */
+static gfxMatrix
+TransformBetweenRects(const gfxRect& aFrom, const gfxRect& aTo)
+{
+  gfxSize scale(aTo.width / aFrom.width,
+                aTo.height / aFrom.height);
+  gfxPoint translation(aTo.x - aFrom.x * scale.width,
+                       aTo.y - aFrom.y * scale.height);
+  return gfxMatrix(scale.width, 0, 0, scale.height,
+                   translation.x, translation.y);
+}
+
+static nsRect
+TileNearRect(const nsRect& aAnyTile, const nsRect& aTargetRect)
+{
+  nsPoint distance = aTargetRect.TopLeft() - aAnyTile.TopLeft();
+  return aAnyTile + nsPoint(distance.x / aAnyTile.width * aAnyTile.width,
+                            distance.y / aAnyTile.height * aAnyTile.height);
+}
+
+static gfxFloat
+StableRound(gfxFloat aValue)
+{
+  // Values slightly less than 0.5 should round up like 0.5 would; we're
+  // assuming they were meant to be 0.5.
+  return floor(aValue + 0.5001);
+}
+
+static gfxPoint
+StableRound(const gfxPoint& aPoint)
+{
+  return gfxPoint(StableRound(aPoint.x), StableRound(aPoint.y));
+}
+
+/**
+ * Given a set of input parameters, compute certain output parameters
+ * for drawing an image with the image snapping algorithm.
+ * See https://wiki.mozilla.org/Gecko:Image_Snapping_and_Rendering
+ *
+ *  @see nsLayoutUtils::DrawImage() for the descriptions of input parameters
+ */
+static SnappedImageDrawingParameters
+ComputeSnappedImageDrawingParameters(gfxContext*     aCtx,
+                                     int32_t         aAppUnitsPerDevPixel,
+                                     const nsRect    aDest,
+                                     const nsRect    aFill,
+                                     const nsPoint   aAnchor,
+                                     const nsRect    aDirty,
+                                     imgIContainer*  aImage,
+                                     const SamplingFilter aSamplingFilter,
+                                     uint32_t        aImageFlags,
+                                     ExtendMode      aExtendMode)
+{
+  if (aDest.IsEmpty() || aFill.IsEmpty())
+    return SnappedImageDrawingParameters();
+
+  // Avoid unnecessarily large offsets.
+  bool doTile = !aDest.Contains(aFill);
+  nsRect appUnitDest = doTile ? TileNearRect(aDest, aFill.Intersect(aDirty))
+                              : aDest;
+  nsPoint anchor = aAnchor + (appUnitDest.TopLeft() - aDest.TopLeft());
+
+  gfxRect devPixelDest =
+    nsLayoutUtils::RectToGfxRect(appUnitDest, aAppUnitsPerDevPixel);
+  gfxRect devPixelFill =
+    nsLayoutUtils::RectToGfxRect(aFill, aAppUnitsPerDevPixel);
+  gfxRect devPixelDirty =
+    nsLayoutUtils::RectToGfxRect(aDirty, aAppUnitsPerDevPixel);
+
+  gfxMatrix currentMatrix = aCtx->CurrentMatrix();
+  gfxRect fill = devPixelFill;
+  gfxRect dest = devPixelDest;
+  bool didSnap;
+  // Snap even if we have a scale in the context. But don't snap if
+  // we have something that's not translation+scale, or if the scale flips in
+  // the X or Y direction, because snapped image drawing can't handle that yet.
+  if (!currentMatrix.HasNonAxisAlignedTransform() &&
+      currentMatrix._11 > 0.0 && currentMatrix._22 > 0.0 &&
+      aCtx->UserToDevicePixelSnapped(fill, true) &&
+      aCtx->UserToDevicePixelSnapped(dest, true)) {
+    // We snapped. On this code path, |fill| and |dest| take into account
+    // currentMatrix's transform.
+    didSnap = true;
+  } else {
+    // We didn't snap. On this code path, |fill| and |dest| do not take into
+    // account currentMatrix's transform.
+    didSnap = false;
+    fill = devPixelFill;
+    dest = devPixelDest;
+  }
+
+  // If we snapped above, |dest| already takes into account |currentMatrix|'s scale
+  // and has integer coordinates. If not, we need these properties to compute
+  // the optimal drawn image size, so compute |snappedDestSize| here.
+  gfxSize snappedDestSize = dest.Size();
+  if (!didSnap) {
+    gfxSize scaleFactors = currentMatrix.ScaleFactors(true);
+    snappedDestSize.Scale(scaleFactors.width, scaleFactors.height);
+    snappedDestSize.width = NS_round(snappedDestSize.width);
+    snappedDestSize.height = NS_round(snappedDestSize.height);
+  }
+
+  // We need to be sure that this is at least one pixel in width and height,
+  // or we'll end up drawing nothing even if we have a nonempty fill.
+  snappedDestSize.width = std::max(snappedDestSize.width, 1.0);
+  snappedDestSize.height = std::max(snappedDestSize.height, 1.0);
+
+  // Bail if we're not going to end up drawing anything.
+  if (fill.IsEmpty() || snappedDestSize.IsEmpty()) {
+    return SnappedImageDrawingParameters();
+  }
+
+  nsIntSize intImageSize =
+    aImage->OptimalImageSizeForDest(snappedDestSize,
+                                    imgIContainer::FRAME_CURRENT,
+                                    aSamplingFilter, aImageFlags);
+  gfxSize imageSize(intImageSize.width, intImageSize.height);
+
+  // XXX(seth): May be buggy; see bug 1151016.
+  CSSIntSize svgViewportSize = currentMatrix.IsIdentity()
+    ? CSSIntSize(intImageSize.width, intImageSize.height)
+    : CSSIntSize::Truncate(devPixelDest.width, devPixelDest.height);
+
+  // Compute the set of pixels that would be sampled by an ideal rendering
+  gfxPoint subimageTopLeft =
+    MapToFloatImagePixels(imageSize, devPixelDest, devPixelFill.TopLeft());
+  gfxPoint subimageBottomRight =
+    MapToFloatImagePixels(imageSize, devPixelDest, devPixelFill.BottomRight());
+  gfxRect subimage;
+  subimage.MoveTo(NSToIntFloor(subimageTopLeft.x),
+                  NSToIntFloor(subimageTopLeft.y));
+  subimage.SizeTo(NSToIntCeil(subimageBottomRight.x) - subimage.x,
+                  NSToIntCeil(subimageBottomRight.y) - subimage.y);
+
+  if (subimage.IsEmpty()) {
+    // Bail if the subimage is empty (we're not going to be drawing anything).
+    return SnappedImageDrawingParameters();
+  }
+
+  gfxMatrix transform;
+  gfxMatrix invTransform;
+
+  bool anchorAtUpperLeft = anchor.x == appUnitDest.x &&
+                           anchor.y == appUnitDest.y;
+  bool exactlyOneImageCopy = aFill.IsEqualEdges(appUnitDest);
+  if (anchorAtUpperLeft && exactlyOneImageCopy) {
+    // The simple case: we can ignore the anchor point and compute the
+    // transformation from the sampled region (the subimage) to the fill rect.
+    // This approach is preferable when it works since it tends to produce
+    // less numerical error.
+    transform = TransformBetweenRects(subimage, fill);
+    invTransform = TransformBetweenRects(fill, subimage);
+  } else {
+    // The more complicated case: we compute the transformation from the
+    // image rect positioned at the image space anchor point to the dest rect
+    // positioned at the device space anchor point.
+
+    // Compute the anchor point in both device space and image space.  This
+    // code assumes that pixel-based devices have one pixel per device unit!
+    gfxPoint anchorPoint(gfxFloat(anchor.x)/aAppUnitsPerDevPixel,
+                         gfxFloat(anchor.y)/aAppUnitsPerDevPixel);
+    gfxPoint imageSpaceAnchorPoint =
+      MapToFloatImagePixels(imageSize, devPixelDest, anchorPoint);
+
+    if (didSnap) {
+      imageSpaceAnchorPoint = StableRound(imageSpaceAnchorPoint);
+      anchorPoint = imageSpaceAnchorPoint;
+      anchorPoint = MapToFloatUserPixels(imageSize, devPixelDest, anchorPoint);
+      anchorPoint = currentMatrix.Transform(anchorPoint);
+      anchorPoint = StableRound(anchorPoint);
+    }
+
+    // Compute an unsnapped version of the dest rect's size. We continue to
+    // follow the pattern that we take |currentMatrix| into account only if
+    // |didSnap| is true.
+    gfxSize unsnappedDestSize
+      = didSnap ? devPixelDest.Size() * currentMatrix.ScaleFactors(true)
+                : devPixelDest.Size();
+
+    gfxRect anchoredDestRect(anchorPoint, unsnappedDestSize);
+    gfxRect anchoredImageRect(imageSpaceAnchorPoint, imageSize);
+
+    // Calculate anchoredDestRect with snapped fill rect when the devPixelFill rect
+    // corresponds to just a single tile in that direction
+    if (fill.Width() != devPixelFill.Width() &&
+        devPixelDest.x == devPixelFill.x &&
+        devPixelDest.XMost() == devPixelFill.XMost()) {
+      anchoredDestRect.width = fill.width;
+    }
+    if (fill.Height() != devPixelFill.Height() &&
+        devPixelDest.y == devPixelFill.y &&
+        devPixelDest.YMost() == devPixelFill.YMost()) {
+      anchoredDestRect.height = fill.height;
+    }
+
+    transform = TransformBetweenRects(anchoredImageRect, anchoredDestRect);
+    invTransform = TransformBetweenRects(anchoredDestRect, anchoredImageRect);
+  }
+
+  // If the transform is not a straight translation by integers, then
+  // filtering will occur, and restricting the fill rect to the dirty rect
+  // would change the values computed for edge pixels, which we can't allow.
+  // Also, if 'didSnap' is false then rounding out 'devPixelDirty' might not
+  // produce pixel-aligned coordinates, which would also break the values
+  // computed for edge pixels.
+  if (didSnap && !invTransform.HasNonIntegerTranslation()) {
+    // This form of Transform is safe to call since non-axis-aligned
+    // transforms wouldn't be snapped.
+    devPixelDirty = currentMatrix.Transform(devPixelDirty);
+    devPixelDirty.RoundOut();
+    fill = fill.Intersect(devPixelDirty);
+  }
+  if (fill.IsEmpty())
+    return SnappedImageDrawingParameters();
+
+  gfxRect imageSpaceFill(didSnap ? invTransform.Transform(fill)
+                                 : invTransform.TransformBounds(fill));
+
+  // If we didn't snap, we need to post-multiply the matrix on the context to
+  // get the final matrix we'll draw with, because we didn't take it into
+  // account when computing the matrices above.
+  if (!didSnap) {
+    transform = transform * currentMatrix;
+  }
+
+  ExtendMode extendMode = (aImageFlags & imgIContainer::FLAG_CLAMP)
+                          ? ExtendMode::CLAMP
+                          : aExtendMode;
+  // We were passed in the default extend mode but need to tile.
+  if (extendMode == ExtendMode::CLAMP && doTile) {
+    MOZ_ASSERT(!(aImageFlags & imgIContainer::FLAG_CLAMP));
+    extendMode = ExtendMode::REPEAT;
+  }
+
+  ImageRegion region =
+    ImageRegion::CreateWithSamplingRestriction(imageSpaceFill, subimage, extendMode);
+
+  return SnappedImageDrawingParameters(transform, intImageSize,
+                                       region, svgViewportSize);
+}
+
+static DrawResult
+DrawImageInternal(gfxContext&            aContext,
+                  nsPresContext*         aPresContext,
+                  imgIContainer*         aImage,
+                  const SamplingFilter   aSamplingFilter,
+                  const nsRect&          aDest,
+                  const nsRect&          aFill,
+                  const nsPoint&         aAnchor,
+                  const nsRect&          aDirty,
+                  const SVGImageContext* aSVGContext,
+                  uint32_t               aImageFlags,
+                  ExtendMode             aExtendMode = ExtendMode::CLAMP)
+{
+  DrawResult result = DrawResult::SUCCESS;
+
+  if (aPresContext->Type() == nsPresContext::eContext_Print) {
+    // We want vector images to be passed on as vector commands, not a raster
+    // image.
+    aImageFlags |= imgIContainer::FLAG_BYPASS_SURFACE_CACHE;
+  }
+  if (aDest.Contains(aFill)) {
+    aImageFlags |= imgIContainer::FLAG_CLAMP;
+  }
+  int32_t appUnitsPerDevPixel =
+   aPresContext->AppUnitsPerDevPixel();
+
+  SnappedImageDrawingParameters params =
+    ComputeSnappedImageDrawingParameters(&aContext, appUnitsPerDevPixel, aDest,
+                                         aFill, aAnchor, aDirty, aImage,
+                                         aSamplingFilter, aImageFlags, aExtendMode);
+
+  if (!params.shouldDraw) {
+    return result;
+  }
+
+  {
+    gfxContextMatrixAutoSaveRestore contextMatrixRestorer(&aContext);
+
+    RefPtr<gfxContext> destCtx = &aContext;
+
+    destCtx->SetMatrix(params.imageSpaceToDeviceSpace);
+
+    Maybe<SVGImageContext> svgContext = ToMaybe(aSVGContext);
+    if (!svgContext) {
+      // Use the default viewport.
+      svgContext = Some(SVGImageContext(params.svgViewportSize, Nothing()));
+    }
+
+    result = aImage->Draw(destCtx, params.size, params.region,
+                          imgIContainer::FRAME_CURRENT, aSamplingFilter,
+                          svgContext, aImageFlags);
+
+  }
+
+  return result;
+}
+
+/* static */ DrawResult
+nsLayoutUtils::DrawSingleUnscaledImage(gfxContext&          aContext,
+                                       nsPresContext*       aPresContext,
+                                       imgIContainer*       aImage,
+                                       const SamplingFilter aSamplingFilter,
+                                       const nsPoint&       aDest,
+                                       const nsRect*        aDirty,
+                                       uint32_t             aImageFlags,
+                                       const nsRect*        aSourceArea)
+{
+  CSSIntSize imageSize;
+  aImage->GetWidth(&imageSize.width);
+  aImage->GetHeight(&imageSize.height);
+  if (imageSize.width < 1 || imageSize.height < 1) {
+    NS_WARNING("Image width or height is non-positive");
+    return DrawResult::TEMPORARY_ERROR;
+  }
+
+  nsSize size(CSSPixel::ToAppUnits(imageSize));
+  nsRect source;
+  if (aSourceArea) {
+    source = *aSourceArea;
+  } else {
+    source.SizeTo(size);
+  }
+
+  nsRect dest(aDest - source.TopLeft(), size);
+  nsRect fill(aDest, source.Size());
+  // Ensure that only a single image tile is drawn. If aSourceArea extends
+  // outside the image bounds, we want to honor the aSourceArea-to-aDest
+  // translation but we don't want to actually tile the image.
+  fill.IntersectRect(fill, dest);
+  return DrawImageInternal(aContext, aPresContext,
+                           aImage, aSamplingFilter,
+                           dest, fill, aDest, aDirty ? *aDirty : dest,
+                           nullptr, aImageFlags);
+}
+
+/* static */ DrawResult
+nsLayoutUtils::DrawSingleImage(gfxContext&            aContext,
+                               nsPresContext*         aPresContext,
+                               imgIContainer*         aImage,
+                               const SamplingFilter   aSamplingFilter,
+                               const nsRect&          aDest,
+                               const nsRect&          aDirty,
+                               const SVGImageContext* aSVGContext,
+                               uint32_t               aImageFlags,
+                               const nsPoint*         aAnchorPoint,
+                               const nsRect*          aSourceArea)
+{
+  nscoord appUnitsPerCSSPixel = nsDeviceContext::AppUnitsPerCSSPixel();
+  CSSIntSize pixelImageSize(ComputeSizeForDrawingWithFallback(aImage, aDest.Size()));
+  if (pixelImageSize.width < 1 || pixelImageSize.height < 1) {
+    NS_WARNING("Image width or height is non-positive");
+    return DrawResult::TEMPORARY_ERROR;
+  }
+
+  nsSize imageSize(CSSPixel::ToAppUnits(pixelImageSize));
+  nsRect source;
+  nsCOMPtr<imgIContainer> image;
+  if (aSourceArea) {
+    source = *aSourceArea;
+    nsIntRect subRect(source.x, source.y, source.width, source.height);
+    subRect.ScaleInverseRoundOut(appUnitsPerCSSPixel);
+    image = ImageOps::Clip(aImage, subRect);
+
+    nsRect imageRect;
+    imageRect.SizeTo(imageSize);
+    nsRect clippedSource = imageRect.Intersect(source);
+
+    source -= clippedSource.TopLeft();
+    imageSize = clippedSource.Size();
+  } else {
+    source.SizeTo(imageSize);
+    image = aImage;
+  }
+
+  nsRect dest = GetWholeImageDestination(imageSize, source, aDest);
+
+  // Ensure that only a single image tile is drawn. If aSourceArea extends
+  // outside the image bounds, we want to honor the aSourceArea-to-aDest
+  // transform but we don't want to actually tile the image.
+  nsRect fill;
+  fill.IntersectRect(aDest, dest);
+  return DrawImageInternal(aContext, aPresContext, image,
+                           aSamplingFilter, dest, fill,
+                           aAnchorPoint ? *aAnchorPoint : fill.TopLeft(),
+                           aDirty, aSVGContext, aImageFlags);
+}
+
+/* static */ void
+nsLayoutUtils::ComputeSizeForDrawing(imgIContainer *aImage,
+                                     CSSIntSize&    aImageSize, /*outparam*/
+                                     nsSize&        aIntrinsicRatio, /*outparam*/
+                                     bool&          aGotWidth,  /*outparam*/
+                                     bool&          aGotHeight  /*outparam*/)
+{
+  aGotWidth  = NS_SUCCEEDED(aImage->GetWidth(&aImageSize.width));
+  aGotHeight = NS_SUCCEEDED(aImage->GetHeight(&aImageSize.height));
+  bool gotRatio = NS_SUCCEEDED(aImage->GetIntrinsicRatio(&aIntrinsicRatio));
+
+  if (!(aGotWidth && aGotHeight) && !gotRatio) {
+    // We hit an error (say, because the image failed to load or couldn't be
+    // decoded) and should return zero size.
+    aGotWidth = aGotHeight = true;
+    aImageSize = CSSIntSize(0, 0);
+    aIntrinsicRatio = nsSize(0, 0);
+  }
+}
+
+/* static */ CSSIntSize
+nsLayoutUtils::ComputeSizeForDrawingWithFallback(imgIContainer* aImage,
+                                                 const nsSize&  aFallbackSize)
+{
+  CSSIntSize imageSize;
+  nsSize imageRatio;
+  bool gotHeight, gotWidth;
+  ComputeSizeForDrawing(aImage, imageSize, imageRatio, gotWidth, gotHeight);
+
+  // If we didn't get both width and height, try to compute them using the
+  // intrinsic ratio of the image.
+  if (gotWidth != gotHeight) {
+    if (!gotWidth) {
+      if (imageRatio.height != 0) {
+        imageSize.width =
+          NSCoordSaturatingNonnegativeMultiply(imageSize.height,
+                                               float(imageRatio.width) /
+                                               float(imageRatio.height));
+        gotWidth = true;
+      }
+    } else {
+      if (imageRatio.width != 0) {
+        imageSize.height =
+          NSCoordSaturatingNonnegativeMultiply(imageSize.width,
+                                               float(imageRatio.height) /
+                                               float(imageRatio.width));
+        gotHeight = true;
+      }
+    }
+  }
+
+  // If we still don't have a width or height, just use the fallback size the
+  // caller provided.
+  if (!gotWidth) {
+    imageSize.width = nsPresContext::AppUnitsToIntCSSPixels(aFallbackSize.width);
+  }
+  if (!gotHeight) {
+    imageSize.height = nsPresContext::AppUnitsToIntCSSPixels(aFallbackSize.height);
+  }
+
+  return imageSize;
+}
+
+/* static */ DrawResult
+nsLayoutUtils::DrawBackgroundImage(gfxContext&         aContext,
+                                   nsPresContext*      aPresContext,
+                                   imgIContainer*      aImage,
+                                   const CSSIntSize&   aImageSize,
+                                   SamplingFilter      aSamplingFilter,
+                                   const nsRect&       aDest,
+                                   const nsRect&       aFill,
+                                   const nsSize&       aRepeatSize,
+                                   const nsPoint&      aAnchor,
+                                   const nsRect&       aDirty,
+                                   uint32_t            aImageFlags,
+                                   ExtendMode          aExtendMode)
+{
+  PROFILER_LABEL("layout", "nsLayoutUtils::DrawBackgroundImage",
+                 js::ProfileEntry::Category::GRAPHICS);
+
+  SVGImageContext svgContext(aImageSize, Nothing());
+
+  /* Fast path when there is no need for image spacing */
+  if (aRepeatSize.width == aDest.width && aRepeatSize.height == aDest.height) {
+    return DrawImageInternal(aContext, aPresContext, aImage,
+                             aSamplingFilter, aDest, aFill, aAnchor,
+                             aDirty, &svgContext, aImageFlags, aExtendMode);
+  }
+
+  nsPoint firstTilePos = aDest.TopLeft() +
+                         nsPoint(NSToIntFloor(float(aFill.x - aDest.x) / aRepeatSize.width) * aRepeatSize.width,
+                                 NSToIntFloor(float(aFill.y - aDest.y) / aRepeatSize.height) * aRepeatSize.height);
+  for (int32_t i = firstTilePos.x; i < aFill.XMost(); i += aRepeatSize.width) {
+    for (int32_t j = firstTilePos.y; j < aFill.YMost(); j += aRepeatSize.height) {
+      nsRect dest(i, j, aDest.width, aDest.height);
+      DrawResult result = DrawImageInternal(aContext, aPresContext, aImage, aSamplingFilter,
+                                            dest, dest, aAnchor, aDirty, &svgContext,
+                                            aImageFlags, ExtendMode::CLAMP);
+      if (result != DrawResult::SUCCESS) {
+        return result;
+      }
+    }
+  }
+
+  return DrawResult::SUCCESS;
+}
+
+/* static */ DrawResult
+nsLayoutUtils::DrawImage(gfxContext&         aContext,
+                         nsPresContext*      aPresContext,
+                         imgIContainer*      aImage,
+                         const SamplingFilter aSamplingFilter,
+                         const nsRect&       aDest,
+                         const nsRect&       aFill,
+                         const nsPoint&      aAnchor,
+                         const nsRect&       aDirty,
+                         uint32_t            aImageFlags)
+{
+  return DrawImageInternal(aContext, aPresContext, aImage,
+                           aSamplingFilter, aDest, aFill, aAnchor,
+                           aDirty, nullptr, aImageFlags);
+}
+
+/* static */ nsRect
+nsLayoutUtils::GetWholeImageDestination(const nsSize& aWholeImageSize,
+                                        const nsRect& aImageSourceArea,
+                                        const nsRect& aDestArea)
+{
+  double scaleX = double(aDestArea.width)/aImageSourceArea.width;
+  double scaleY = double(aDestArea.height)/aImageSourceArea.height;
+  nscoord destOffsetX = NSToCoordRound(aImageSourceArea.x*scaleX);
+  nscoord destOffsetY = NSToCoordRound(aImageSourceArea.y*scaleY);
+  nscoord wholeSizeX = NSToCoordRound(aWholeImageSize.width*scaleX);
+  nscoord wholeSizeY = NSToCoordRound(aWholeImageSize.height*scaleY);
+  return nsRect(aDestArea.TopLeft() - nsPoint(destOffsetX, destOffsetY),
+                nsSize(wholeSizeX, wholeSizeY));
+}
+
+/* static */ already_AddRefed<imgIContainer>
+nsLayoutUtils::OrientImage(imgIContainer* aContainer,
+                           const nsStyleImageOrientation& aOrientation)
+{
+  MOZ_ASSERT(aContainer, "Should have an image container");
+  nsCOMPtr<imgIContainer> img(aContainer);
+
+  if (aOrientation.IsFromImage()) {
+    img = ImageOps::Orient(img, img->GetOrientation());
+  } else if (!aOrientation.IsDefault()) {
+    Angle angle = aOrientation.Angle();
+    Flip flip  = aOrientation.IsFlipped() ? Flip::Horizontal
+                                          : Flip::Unflipped;
+    img = ImageOps::Orient(img, Orientation(angle, flip));
+  }
+
+  return img.forget();
+}
+
+static bool NonZeroStyleCoord(const nsStyleCoord& aCoord)
+{
+  if (aCoord.IsCoordPercentCalcUnit()) {
+    // Since negative results are clamped to 0, check > 0.
+    return nsRuleNode::ComputeCoordPercentCalc(aCoord, nscoord_MAX) > 0 ||
+           nsRuleNode::ComputeCoordPercentCalc(aCoord, 0) > 0;
+  }
+
+  return true;
+}
+
+/* static */ bool
+nsLayoutUtils::HasNonZeroCorner(const nsStyleCorners& aCorners)
+{
+  NS_FOR_CSS_HALF_CORNERS(corner) {
+    if (NonZeroStyleCoord(aCorners.Get(corner)))
+      return true;
+  }
+  return false;
+}
+
+// aCorner is a "full corner" value, i.e. NS_CORNER_TOP_LEFT etc
+static bool IsCornerAdjacentToSide(uint8_t aCorner, css::Side aSide)
+{
+  static_assert((int)NS_SIDE_TOP == NS_CORNER_TOP_LEFT, "Check for Full Corner");
+  static_assert((int)NS_SIDE_RIGHT == NS_CORNER_TOP_RIGHT, "Check for Full Corner");
+  static_assert((int)NS_SIDE_BOTTOM == NS_CORNER_BOTTOM_RIGHT, "Check for Full Corner");
+  static_assert((int)NS_SIDE_LEFT == NS_CORNER_BOTTOM_LEFT, "Check for Full Corner");
+  static_assert((int)NS_SIDE_TOP == ((NS_CORNER_TOP_RIGHT - 1)&3), "Check for Full Corner");
+  static_assert((int)NS_SIDE_RIGHT == ((NS_CORNER_BOTTOM_RIGHT - 1)&3), "Check for Full Corner");
+  static_assert((int)NS_SIDE_BOTTOM == ((NS_CORNER_BOTTOM_LEFT - 1)&3), "Check for Full Corner");
+  static_assert((int)NS_SIDE_LEFT == ((NS_CORNER_TOP_LEFT - 1)&3), "Check for Full Corner");
+
+  return aSide == aCorner || aSide == ((aCorner - 1)&3);
+}
+
+/* static */ bool
+nsLayoutUtils::HasNonZeroCornerOnSide(const nsStyleCorners& aCorners,
+                                      css::Side aSide)
+{
+  static_assert(NS_CORNER_TOP_LEFT_X/2 == NS_CORNER_TOP_LEFT, "Check for Non Zero on side");
+  static_assert(NS_CORNER_TOP_LEFT_Y/2 == NS_CORNER_TOP_LEFT, "Check for Non Zero on side");
+  static_assert(NS_CORNER_TOP_RIGHT_X/2 == NS_CORNER_TOP_RIGHT, "Check for Non Zero on side");
+  static_assert(NS_CORNER_TOP_RIGHT_Y/2 == NS_CORNER_TOP_RIGHT, "Check for Non Zero on side");
+  static_assert(NS_CORNER_BOTTOM_RIGHT_X/2 == NS_CORNER_BOTTOM_RIGHT, "Check for Non Zero on side");
+  static_assert(NS_CORNER_BOTTOM_RIGHT_Y/2 == NS_CORNER_BOTTOM_RIGHT, "Check for Non Zero on side");
+  static_assert(NS_CORNER_BOTTOM_LEFT_X/2 == NS_CORNER_BOTTOM_LEFT, "Check for Non Zero on side");
+  static_assert(NS_CORNER_BOTTOM_LEFT_Y/2 == NS_CORNER_BOTTOM_LEFT, "Check for Non Zero on side");
+
+  NS_FOR_CSS_HALF_CORNERS(corner) {
+    // corner is a "half corner" value, so dividing by two gives us a
+    // "full corner" value.
+    if (NonZeroStyleCoord(aCorners.Get(corner)) &&
+        IsCornerAdjacentToSide(corner/2, aSide))
+      return true;
+  }
+  return false;
+}
+
+/* static */ nsTransparencyMode
+nsLayoutUtils::GetFrameTransparency(nsIFrame* aBackgroundFrame,
+                                    nsIFrame* aCSSRootFrame) {
+  if (aCSSRootFrame->StyleEffects()->mOpacity < 1.0f)
+    return eTransparencyTransparent;
+
+  if (HasNonZeroCorner(aCSSRootFrame->StyleBorder()->mBorderRadius))
+    return eTransparencyTransparent;
+
+  if (aCSSRootFrame->StyleDisplay()->mAppearance == NS_THEME_WIN_GLASS)
+    return eTransparencyGlass;
+
+  if (aCSSRootFrame->StyleDisplay()->mAppearance == NS_THEME_WIN_BORDERLESS_GLASS)
+    return eTransparencyBorderlessGlass;
+
+  nsITheme::Transparency transparency;
+  if (aCSSRootFrame->IsThemed(&transparency))
+    return transparency == nsITheme::eTransparent
+         ? eTransparencyTransparent
+         : eTransparencyOpaque;
+
+  // We need an uninitialized window to be treated as opaque because
+  // doing otherwise breaks window display effects on some platforms,
+  // specifically Vista. (bug 450322)
+  if (aBackgroundFrame->GetType() == nsGkAtoms::viewportFrame &&
+      !aBackgroundFrame->PrincipalChildList().FirstChild()) {
+    return eTransparencyOpaque;
+  }
+
+  nsStyleContext* bgSC;
+  if (!nsCSSRendering::FindBackground(aBackgroundFrame, &bgSC)) {
+    return eTransparencyTransparent;
+  }
+  const nsStyleBackground* bg = bgSC->StyleBackground();
+  if (NS_GET_A(bg->mBackgroundColor) < 255 ||
+      // bottom layer's clip is used for the color
+      bg->BottomLayer().mClip != NS_STYLE_IMAGELAYER_CLIP_BORDER)
+    return eTransparencyTransparent;
+  return eTransparencyOpaque;
+}
+
+static bool IsPopupFrame(nsIFrame* aFrame)
+{
+  // aFrame is a popup it's the list control frame dropdown for a combobox.
+  nsIAtom* frameType = aFrame->GetType();
+  if (frameType == nsGkAtoms::listControlFrame) {
+    nsListControlFrame* lcf = static_cast<nsListControlFrame*>(aFrame);
+    return lcf->IsInDropDownMode();
+  }
+
+  // ... or if it's a XUL menupopup frame.
+  return frameType == nsGkAtoms::menuPopupFrame;
+}
+
+/* static */ bool
+nsLayoutUtils::IsPopup(nsIFrame* aFrame)
+{
+  // Optimization: the frame can't possibly be a popup if it has no view.
+  if (!aFrame->HasView()) {
+    NS_ASSERTION(!IsPopupFrame(aFrame), "popup frame must have a view");
+    return false;
+  }
+  return IsPopupFrame(aFrame);
+}
+
+/* static */ nsIFrame*
+nsLayoutUtils::GetDisplayRootFrame(nsIFrame* aFrame)
+{
+  // We could use GetRootPresContext() here if the
+  // NS_FRAME_IN_POPUP frame bit is set.
+  nsIFrame* f = aFrame;
+  for (;;) {
+    if (!f->HasAnyStateBits(NS_FRAME_IN_POPUP)) {
+      f = f->PresContext()->FrameManager()->GetRootFrame();
+    } else if (IsPopup(f)) {
+      return f;
+    }
+    nsIFrame* parent = GetCrossDocParentFrame(f);
+    if (!parent)
+      return f;
+    f = parent;
+  }
+}
+
+/* static */ nsIFrame*
+nsLayoutUtils::GetReferenceFrame(nsIFrame* aFrame)
+{
+  nsIFrame *f = aFrame;
+  for (;;) {
+    if (f->IsTransformed() || f->IsPreserve3DLeaf() || IsPopup(f)) {
+      return f;
+    }
+    nsIFrame* parent = GetCrossDocParentFrame(f);
+    if (!parent) {
+      return f;
+    }
+    f = parent;
+  }
+}
+
+/* static */ uint32_t
+nsLayoutUtils::GetTextRunFlagsForStyle(nsStyleContext* aStyleContext,
+                                       const nsStyleFont* aStyleFont,
+                                       const nsStyleText* aStyleText,
+                                       nscoord aLetterSpacing)
+{
+  uint32_t result = 0;
+  if (aLetterSpacing != 0) {
+    result |= gfxTextRunFactory::TEXT_DISABLE_OPTIONAL_LIGATURES;
+  }
+  if (aStyleText->mControlCharacterVisibility == NS_STYLE_CONTROL_CHARACTER_VISIBILITY_HIDDEN) {
+    result |= gfxTextRunFactory::TEXT_HIDE_CONTROL_CHARACTERS;
+  }
+  switch (aStyleContext->StyleText()->mTextRendering) {
+  case NS_STYLE_TEXT_RENDERING_OPTIMIZESPEED:
+    result |= gfxTextRunFactory::TEXT_OPTIMIZE_SPEED;
+    break;
+  case NS_STYLE_TEXT_RENDERING_AUTO:
+    if (aStyleFont->mFont.size <
+        aStyleContext->PresContext()->GetAutoQualityMinFontSize()) {
+      result |= gfxTextRunFactory::TEXT_OPTIMIZE_SPEED;
+    }
+    break;
+  default:
+    break;
+  }
+  return result | GetTextRunOrientFlagsForStyle(aStyleContext);
+}
+
+/* static */ uint32_t
+nsLayoutUtils::GetTextRunOrientFlagsForStyle(nsStyleContext* aStyleContext)
+{
+  uint8_t writingMode = aStyleContext->StyleVisibility()->mWritingMode;
+  switch (writingMode) {
+  case NS_STYLE_WRITING_MODE_HORIZONTAL_TB:
+    return gfxTextRunFactory::TEXT_ORIENT_HORIZONTAL;
+
+  case NS_STYLE_WRITING_MODE_VERTICAL_LR:
+  case NS_STYLE_WRITING_MODE_VERTICAL_RL:
+    switch (aStyleContext->StyleVisibility()->mTextOrientation) {
+    case NS_STYLE_TEXT_ORIENTATION_MIXED:
+      return gfxTextRunFactory::TEXT_ORIENT_VERTICAL_MIXED;
+    case NS_STYLE_TEXT_ORIENTATION_UPRIGHT:
+      return gfxTextRunFactory::TEXT_ORIENT_VERTICAL_UPRIGHT;
+    case NS_STYLE_TEXT_ORIENTATION_SIDEWAYS:
+      return gfxTextRunFactory::TEXT_ORIENT_VERTICAL_SIDEWAYS_RIGHT;
+    default:
+      NS_NOTREACHED("unknown text-orientation");
+      return 0;
+    }
+
+  case NS_STYLE_WRITING_MODE_SIDEWAYS_LR:
+    return gfxTextRunFactory::TEXT_ORIENT_VERTICAL_SIDEWAYS_LEFT;
+
+  case NS_STYLE_WRITING_MODE_SIDEWAYS_RL:
+    return gfxTextRunFactory::TEXT_ORIENT_VERTICAL_SIDEWAYS_RIGHT;
+
+  default:
+    NS_NOTREACHED("unknown writing-mode");
+    return 0;
+  }
+}
+
+/* static */ void
+nsLayoutUtils::GetRectDifferenceStrips(const nsRect& aR1, const nsRect& aR2,
+                                       nsRect* aHStrip, nsRect* aVStrip) {
+  NS_ASSERTION(aR1.TopLeft() == aR2.TopLeft(),
+               "expected rects at the same position");
+  nsRect unionRect(aR1.x, aR1.y, std::max(aR1.width, aR2.width),
+                   std::max(aR1.height, aR2.height));
+  nscoord VStripStart = std::min(aR1.width, aR2.width);
+  nscoord HStripStart = std::min(aR1.height, aR2.height);
+  *aVStrip = unionRect;
+  aVStrip->x += VStripStart;
+  aVStrip->width -= VStripStart;
+  *aHStrip = unionRect;
+  aHStrip->y += HStripStart;
+  aHStrip->height -= HStripStart;
+}
+
+nsDeviceContext*
+nsLayoutUtils::GetDeviceContextForScreenInfo(nsPIDOMWindowOuter* aWindow)
+{
+  if (!aWindow) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = aWindow->GetDocShell();
+  while (docShell) {
+    // Now make sure our size is up to date.  That will mean that the device
+    // context does the right thing on multi-monitor systems when we return it to
+    // the caller.  It will also make sure that our prescontext has been created,
+    // if we're supposed to have one.
+    nsCOMPtr<nsPIDOMWindowOuter> win = docShell->GetWindow();
+    if (!win) {
+      // No reason to go on
+      return nullptr;
+    }
+
+    win->EnsureSizeUpToDate();
+
+    RefPtr<nsPresContext> presContext;
+    docShell->GetPresContext(getter_AddRefs(presContext));
+    if (presContext) {
+      nsDeviceContext* context = presContext->DeviceContext();
+      if (context) {
+        return context;
+      }
+    }
+
+    nsCOMPtr<nsIDocShellTreeItem> parentItem;
+    docShell->GetParent(getter_AddRefs(parentItem));
+    docShell = do_QueryInterface(parentItem);
+  }
+
+  return nullptr;
+}
+
+/* static */ bool
+nsLayoutUtils::IsReallyFixedPos(nsIFrame* aFrame)
+{
+  NS_PRECONDITION(aFrame->GetParent(),
+                  "IsReallyFixedPos called on frame not in tree");
+  NS_PRECONDITION(aFrame->StyleDisplay()->mPosition ==
+                    NS_STYLE_POSITION_FIXED,
+                  "IsReallyFixedPos called on non-'position:fixed' frame");
+
+  nsIAtom *parentType = aFrame->GetParent()->GetType();
+  return parentType == nsGkAtoms::viewportFrame ||
+         parentType == nsGkAtoms::pageContentFrame;
+}
+
+nsLayoutUtils::SurfaceFromElementResult
+nsLayoutUtils::SurfaceFromOffscreenCanvas(OffscreenCanvas* aOffscreenCanvas,
+                                          uint32_t aSurfaceFlags,
+                                          RefPtr<DrawTarget>& aTarget)
+{
+  SurfaceFromElementResult result;
+
+  bool* isPremultiplied = nullptr;
+  if (aSurfaceFlags & SFE_PREFER_NO_PREMULTIPLY_ALPHA) {
+    isPremultiplied = &result.mIsPremultiplied;
+  }
+
+  nsIntSize size = aOffscreenCanvas->GetWidthHeight();
+
+  result.mSourceSurface = aOffscreenCanvas->GetSurfaceSnapshot(isPremultiplied);
+    if (!result.mSourceSurface) {
+      // If the element doesn't have a context then we won't get a snapshot. The canvas spec wants us to not error and just
+      // draw nothing, so return an empty surface.
+      DrawTarget *ref = aTarget ? aTarget.get() : gfxPlatform::GetPlatform()->ScreenReferenceDrawTarget();
+      RefPtr<DrawTarget> dt = ref->CreateSimilarDrawTarget(IntSize(size.width, size.height),
+                                                           SurfaceFormat::B8G8R8A8);
+    if (dt) {
+      result.mSourceSurface = dt->Snapshot();
+    }
+  } else if (aTarget) {
+    RefPtr<SourceSurface> opt = aTarget->OptimizeSourceSurface(result.mSourceSurface);
+    if (opt) {
+      result.mSourceSurface = opt;
+    }
+  }
+
+  result.mHasSize = true;
+  result.mSize = size;
+  result.mIsWriteOnly = aOffscreenCanvas->IsWriteOnly();
+
+  return result;
+}
+
+nsLayoutUtils::SurfaceFromElementResult
+nsLayoutUtils::SurfaceFromElement(nsIImageLoadingContent* aElement,
+                                  uint32_t aSurfaceFlags,
+                                  RefPtr<DrawTarget>& aTarget)
+{
+  SurfaceFromElementResult result;
+  nsresult rv;
+
+  nsCOMPtr<imgIRequest> imgRequest;
+  rv = aElement->GetRequest(nsIImageLoadingContent::CURRENT_REQUEST,
+                            getter_AddRefs(imgRequest));
+  if (NS_FAILED(rv)) {
+    return result;
+  }
+
+  if (!imgRequest) {
+    // There's no image request. This is either because a request for
+    // a non-empty URI failed, or the URI is the empty string.
+    nsCOMPtr<nsIURI> currentURI;
+    aElement->GetCurrentURI(getter_AddRefs(currentURI));
+    if (!currentURI) {
+      // Treat the empty URI as available instead of broken state.
+      result.mHasSize = true;
+    }
+    return result;
+  }
+
+  uint32_t status;
+  imgRequest->GetImageStatus(&status);
+  result.mHasSize = status & imgIRequest::STATUS_SIZE_AVAILABLE;
+  if ((status & imgIRequest::STATUS_LOAD_COMPLETE) == 0) {
+    // Spec says to use GetComplete, but that only works on
+    // nsIDOMHTMLImageElement, and we support all sorts of other stuff
+    // here.  Do this for now pending spec clarification.
+    result.mIsStillLoading = (status & imgIRequest::STATUS_ERROR) == 0;
+    return result;
+  }
+
+  nsCOMPtr<nsIPrincipal> principal;
+  rv = imgRequest->GetImagePrincipal(getter_AddRefs(principal));
+  if (NS_FAILED(rv)) {
+    return result;
+  }
+
+  nsCOMPtr<imgIContainer> imgContainer;
+  rv = imgRequest->GetImage(getter_AddRefs(imgContainer));
+  if (NS_FAILED(rv)) {
+    return result;
+  }
+
+  uint32_t noRasterize = aSurfaceFlags & SFE_NO_RASTERIZING_VECTORS;
+
+  uint32_t whichFrame = (aSurfaceFlags & SFE_WANT_FIRST_FRAME)
+                        ? (uint32_t) imgIContainer::FRAME_FIRST
+                        : (uint32_t) imgIContainer::FRAME_CURRENT;
+  uint32_t frameFlags = imgIContainer::FLAG_SYNC_DECODE;
+  if (aSurfaceFlags & SFE_NO_COLORSPACE_CONVERSION)
+    frameFlags |= imgIContainer::FLAG_DECODE_NO_COLORSPACE_CONVERSION;
+  if (aSurfaceFlags & SFE_PREFER_NO_PREMULTIPLY_ALPHA) {
+    frameFlags |= imgIContainer::FLAG_DECODE_NO_PREMULTIPLY_ALPHA;
+    result.mIsPremultiplied = false;
+  }
+
+  int32_t imgWidth, imgHeight;
+  nsCOMPtr<nsIContent> content = do_QueryInterface(aElement);
+  HTMLImageElement* element = HTMLImageElement::FromContentOrNull(content);
+  if (aSurfaceFlags & SFE_USE_ELEMENT_SIZE_IF_VECTOR &&
+      element &&
+      imgContainer->GetType() == imgIContainer::TYPE_VECTOR) {
+    imgWidth = element->Width();
+    imgHeight = element->Height();
+  } else {
+    rv = imgContainer->GetWidth(&imgWidth);
+    nsresult rv2 = imgContainer->GetHeight(&imgHeight);
+    if (NS_FAILED(rv) || NS_FAILED(rv2))
+      return result;
+  }
+  result.mSize = IntSize(imgWidth, imgHeight);
+
+  if (!noRasterize || imgContainer->GetType() == imgIContainer::TYPE_RASTER) {
+    if (aSurfaceFlags & SFE_WANT_IMAGE_SURFACE) {
+      frameFlags |= imgIContainer::FLAG_WANT_DATA_SURFACE;
+    }
+    result.mSourceSurface = imgContainer->GetFrameAtSize(result.mSize, whichFrame, frameFlags);
+    if (!result.mSourceSurface) {
+      return result;
+    }
+    // The surface we return is likely to be cached. We don't want to have to
+    // convert to a surface that's compatible with aTarget each time it's used
+    // (that would result in terrible performance), so we convert once here
+    // upfront if aTarget is specified.
+    if (aTarget) {
+      RefPtr<SourceSurface> optSurface =
+        aTarget->OptimizeSourceSurface(result.mSourceSurface);
+      if (optSurface) {
+        result.mSourceSurface = optSurface;
+      }
+    }
+  } else {
+    result.mDrawInfo.mImgContainer = imgContainer;
+    result.mDrawInfo.mWhichFrame = whichFrame;
+    result.mDrawInfo.mDrawingFlags = frameFlags;
+  }
+
+  int32_t corsmode;
+  if (NS_SUCCEEDED(imgRequest->GetCORSMode(&corsmode))) {
+    result.mCORSUsed = (corsmode != imgIRequest::CORS_NONE);
+  }
+
+  result.mPrincipal = principal.forget();
+  // no images, including SVG images, can load content from another domain.
+  result.mIsWriteOnly = false;
+  result.mImageRequest = imgRequest.forget();
+  return result;
+}
+
+nsLayoutUtils::SurfaceFromElementResult
+nsLayoutUtils::SurfaceFromElement(HTMLImageElement *aElement,
+                                  uint32_t aSurfaceFlags,
+                                  RefPtr<DrawTarget>& aTarget)
+{
+  return SurfaceFromElement(static_cast<nsIImageLoadingContent*>(aElement),
+                            aSurfaceFlags, aTarget);
+}
+
+nsLayoutUtils::SurfaceFromElementResult
+nsLayoutUtils::SurfaceFromElement(HTMLCanvasElement* aElement,
+                                  uint32_t aSurfaceFlags,
+                                  RefPtr<DrawTarget>& aTarget)
+{
+  SurfaceFromElementResult result;
+
+  bool* isPremultiplied = nullptr;
+  if (aSurfaceFlags & SFE_PREFER_NO_PREMULTIPLY_ALPHA) {
+    isPremultiplied = &result.mIsPremultiplied;
+  }
+
+  IntSize size = aElement->GetSize();
+
+  result.mSourceSurface = aElement->GetSurfaceSnapshot(isPremultiplied);
+  if (!result.mSourceSurface) {
+     // If the element doesn't have a context then we won't get a snapshot. The canvas spec wants us to not error and just
+     // draw nothing, so return an empty surface.
+     DrawTarget *ref = aTarget ? aTarget.get() : gfxPlatform::GetPlatform()->ScreenReferenceDrawTarget();
+     RefPtr<DrawTarget> dt = ref->CreateSimilarDrawTarget(IntSize(size.width, size.height),
+                                                          SurfaceFormat::B8G8R8A8);
+     if (dt) {
+       result.mSourceSurface = dt->Snapshot();
+     }
+  } else if (aTarget) {
+    RefPtr<SourceSurface> opt = aTarget->OptimizeSourceSurface(result.mSourceSurface);
+    if (opt) {
+      result.mSourceSurface = opt;
+    }
+  }
+
+  // Ensure that any future changes to the canvas trigger proper invalidation,
+  // in case this is being used by -moz-element()
+  aElement->MarkContextClean();
+
+  result.mHasSize = true;
+  result.mSize = size;
+  result.mPrincipal = aElement->NodePrincipal();
+  result.mIsWriteOnly = aElement->IsWriteOnly();
+
+  return result;
+}
+
+nsLayoutUtils::SurfaceFromElementResult
+nsLayoutUtils::SurfaceFromElement(HTMLVideoElement* aElement,
+                                  uint32_t aSurfaceFlags,
+                                  RefPtr<DrawTarget>& aTarget)
+{
+  SurfaceFromElementResult result;
+
+  NS_WARNING_ASSERTION(
+    (aSurfaceFlags & SFE_PREFER_NO_PREMULTIPLY_ALPHA) == 0,
+    "We can't support non-premultiplied alpha for video!");
+
+  if (aElement->ContainsRestrictedContent()) {
+    return result;
+  }
+
+  uint16_t readyState;
+  if (NS_SUCCEEDED(aElement->GetReadyState(&readyState)) &&
+      (readyState == nsIDOMHTMLMediaElement::HAVE_NOTHING ||
+       readyState == nsIDOMHTMLMediaElement::HAVE_METADATA)) {
+    result.mIsStillLoading = true;
+    return result;
+  }
+
+  // If it doesn't have a principal, just bail
+  nsCOMPtr<nsIPrincipal> principal = aElement->GetCurrentVideoPrincipal();
+  if (!principal)
+    return result;
+
+  ImageContainer* container = aElement->GetImageContainer();
+  if (!container)
+    return result;
+
+  AutoLockImage lockImage(container);
+
+  result.mLayersImage = lockImage.GetImage();
+  if (!result.mLayersImage)
+    return result;
+
+  if (aTarget) {
+    // They gave us a DrawTarget to optimize for, so even though we have a layers::Image,
+    // we should unconditionally grab a SourceSurface and try to optimize it.
+    result.mSourceSurface = result.mLayersImage->GetAsSourceSurface();
+    if (!result.mSourceSurface)
+      return result;
+
+    RefPtr<SourceSurface> opt = aTarget->OptimizeSourceSurface(result.mSourceSurface);
+    if (opt) {
+      result.mSourceSurface = opt;
+    }
+  }
+
+  result.mCORSUsed = aElement->GetCORSMode() != CORS_NONE;
+  result.mHasSize = true;
+  result.mSize = result.mLayersImage->GetSize();
+  result.mPrincipal = principal.forget();
+  result.mIsWriteOnly = false;
+
+  return result;
+}
+
+nsLayoutUtils::SurfaceFromElementResult
+nsLayoutUtils::SurfaceFromElement(dom::Element* aElement,
+                                  uint32_t aSurfaceFlags,
+                                  RefPtr<DrawTarget>& aTarget)
+{
+  // If it's a <canvas>, we may be able to just grab its internal surface
+  if (HTMLCanvasElement* canvas =
+        HTMLCanvasElement::FromContentOrNull(aElement)) {
+    return SurfaceFromElement(canvas, aSurfaceFlags, aTarget);
+  }
+
+  // Maybe it's <video>?
+  if (HTMLVideoElement* video =
+        HTMLVideoElement::FromContentOrNull(aElement)) {
+    return SurfaceFromElement(video, aSurfaceFlags, aTarget);
+  }
+
+  // Finally, check if it's a normal image
+  nsCOMPtr<nsIImageLoadingContent> imageLoader = do_QueryInterface(aElement);
+
+  if (!imageLoader) {
+    return SurfaceFromElementResult();
+  }
+
+  return SurfaceFromElement(imageLoader, aSurfaceFlags, aTarget);
+}
+
+/* static */
+nsIContent*
+nsLayoutUtils::GetEditableRootContentByContentEditable(nsIDocument* aDocument)
+{
+  // If the document is in designMode we should return nullptr.
+  if (!aDocument || aDocument->HasFlag(NODE_IS_EDITABLE)) {
+    return nullptr;
+  }
+
+  // contenteditable only works with HTML document.
+  // Note: Use nsIDOMHTMLDocument rather than nsIHTMLDocument for getting the
+  //       body node because nsIDOMHTMLDocument::GetBody() does something
+  //       additional work for some cases and EditorBase uses them.
+  nsCOMPtr<nsIDOMHTMLDocument> domHTMLDoc = do_QueryInterface(aDocument);
+  if (!domHTMLDoc) {
+    return nullptr;
+  }
+
+  Element* rootElement = aDocument->GetRootElement();
+  if (rootElement && rootElement->IsEditable()) {
+    return rootElement;
+  }
+
+  // If there are no editable root element, check its <body> element.
+  // Note that the body element could be <frameset> element.
+  nsCOMPtr<nsIDOMHTMLElement> body;
+  nsresult rv = domHTMLDoc->GetBody(getter_AddRefs(body));
+  nsCOMPtr<nsIContent> content = do_QueryInterface(body);
+  if (NS_SUCCEEDED(rv) && content && content->IsEditable()) {
+    return content;
+  }
+  return nullptr;
+}
+
+#ifdef DEBUG
+/* static */ void
+nsLayoutUtils::AssertNoDuplicateContinuations(nsIFrame* aContainer,
+                                              const nsFrameList& aFrameList)
+{
+  for (nsIFrame* f : aFrameList) {
+    // Check only later continuations of f; we deal with checking the
+    // earlier continuations when we hit those earlier continuations in
+    // the frame list.
+    for (nsIFrame *c = f; (c = c->GetNextInFlow());) {
+      NS_ASSERTION(c->GetParent() != aContainer ||
+                   !aFrameList.ContainsFrame(c),
+                   "Two continuations of the same frame in the same "
+                   "frame list");
+    }
+  }
+}
+
+// Is one of aFrame's ancestors a letter frame?
+static bool
+IsInLetterFrame(nsIFrame *aFrame)
+{
+  for (nsIFrame *f = aFrame->GetParent(); f; f = f->GetParent()) {
+    if (f->GetType() == nsGkAtoms::letterFrame) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/* static */ void
+nsLayoutUtils::AssertTreeOnlyEmptyNextInFlows(nsIFrame *aSubtreeRoot)
+{
+  NS_ASSERTION(aSubtreeRoot->GetPrevInFlow(),
+               "frame tree not empty, but caller reported complete status");
+
+  // Also assert that text frames map no text.
+  int32_t start, end;
+  nsresult rv = aSubtreeRoot->GetOffsets(start, end);
+  NS_ASSERTION(NS_SUCCEEDED(rv), "GetOffsets failed");
+  // In some cases involving :first-letter, we'll partially unlink a
+  // continuation in the middle of a continuation chain from its
+  // previous and next continuations before destroying it, presumably so
+  // that we don't also destroy the later continuations.  Once we've
+  // done this, GetOffsets returns incorrect values.
+  // For examples, see list of tests in
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=619021#c29
+  NS_ASSERTION(start == end || IsInLetterFrame(aSubtreeRoot),
+               "frame tree not empty, but caller reported complete status");
+
+  nsIFrame::ChildListIterator lists(aSubtreeRoot);
+  for (; !lists.IsDone(); lists.Next()) {
+    nsFrameList::Enumerator childFrames(lists.CurrentList());
+    for (; !childFrames.AtEnd(); childFrames.Next()) {
+      nsLayoutUtils::AssertTreeOnlyEmptyNextInFlows(childFrames.get());
+    }
+  }
+}
+#endif
+
+static void
+GetFontFacesForFramesInner(nsIFrame* aFrame, nsFontFaceList* aFontFaceList)
+{
+  NS_PRECONDITION(aFrame, "NULL frame pointer");
+
+  if (aFrame->GetType() == nsGkAtoms::textFrame) {
+    if (!aFrame->GetPrevContinuation()) {
+      nsLayoutUtils::GetFontFacesForText(aFrame, 0, INT32_MAX, true,
+                                         aFontFaceList);
+    }
+    return;
+  }
+
+  nsIFrame::ChildListID childLists[] = { nsIFrame::kPrincipalList,
+                                         nsIFrame::kPopupList };
+  for (size_t i = 0; i < ArrayLength(childLists); ++i) {
+    nsFrameList children(aFrame->GetChildList(childLists[i]));
+    for (nsFrameList::Enumerator e(children); !e.AtEnd(); e.Next()) {
+      nsIFrame* child = e.get();
+      child = nsPlaceholderFrame::GetRealFrameFor(child);
+      GetFontFacesForFramesInner(child, aFontFaceList);
+    }
+  }
+}
+
+/* static */
+nsresult
+nsLayoutUtils::GetFontFacesForFrames(nsIFrame* aFrame,
+                                     nsFontFaceList* aFontFaceList)
+{
+  NS_PRECONDITION(aFrame, "NULL frame pointer");
+
+  while (aFrame) {
+    GetFontFacesForFramesInner(aFrame, aFontFaceList);
+    aFrame = GetNextContinuationOrIBSplitSibling(aFrame);
+  }
+
+  return NS_OK;
+}
+
+/* static */
+nsresult
+nsLayoutUtils::GetFontFacesForText(nsIFrame* aFrame,
+                                   int32_t aStartOffset, int32_t aEndOffset,
+                                   bool aFollowContinuations,
+                                   nsFontFaceList* aFontFaceList)
+{
+  NS_PRECONDITION(aFrame, "NULL frame pointer");
+
+  if (aFrame->GetType() != nsGkAtoms::textFrame) {
+    return NS_OK;
+  }
+
+  nsTextFrame* curr = static_cast<nsTextFrame*>(aFrame);
+  do {
+    int32_t fstart = std::max(curr->GetContentOffset(), aStartOffset);
+    int32_t fend = std::min(curr->GetContentEnd(), aEndOffset);
+    if (fstart >= fend) {
+      curr = static_cast<nsTextFrame*>(curr->GetNextContinuation());
+      continue;
+    }
+
+    // curr is overlapping with the offset we want
+    gfxSkipCharsIterator iter = curr->EnsureTextRun(nsTextFrame::eInflated);
+    gfxTextRun* textRun = curr->GetTextRun(nsTextFrame::eInflated);
+    NS_ENSURE_TRUE(textRun, NS_ERROR_OUT_OF_MEMORY);
+
+    // include continuations in the range that share the same textrun
+    nsTextFrame* next = nullptr;
+    if (aFollowContinuations && fend < aEndOffset) {
+      next = static_cast<nsTextFrame*>(curr->GetNextContinuation());
+      while (next && next->GetTextRun(nsTextFrame::eInflated) == textRun) {
+        fend = std::min(next->GetContentEnd(), aEndOffset);
+        next = fend < aEndOffset ?
+          static_cast<nsTextFrame*>(next->GetNextContinuation()) : nullptr;
+      }
+    }
+
+    uint32_t skipStart = iter.ConvertOriginalToSkipped(fstart);
+    uint32_t skipEnd = iter.ConvertOriginalToSkipped(fend);
+    aFontFaceList->AddFontsFromTextRun(textRun, skipStart, skipEnd - skipStart);
+    curr = next;
+  } while (aFollowContinuations && curr);
+
+  return NS_OK;
+}
+
+/* static */
+size_t
+nsLayoutUtils::SizeOfTextRunsForFrames(nsIFrame* aFrame,
+                                       MallocSizeOf aMallocSizeOf,
+                                       bool clear)
+{
+  NS_PRECONDITION(aFrame, "NULL frame pointer");
+
+  size_t total = 0;
+
+  if (aFrame->GetType() == nsGkAtoms::textFrame) {
+    nsTextFrame* textFrame = static_cast<nsTextFrame*>(aFrame);
+    for (uint32_t i = 0; i < 2; ++i) {
+      gfxTextRun *run = textFrame->GetTextRun(
+        (i != 0) ? nsTextFrame::eInflated : nsTextFrame::eNotInflated);
+      if (run) {
+        if (clear) {
+          run->ResetSizeOfAccountingFlags();
+        } else {
+          total += run->MaybeSizeOfIncludingThis(aMallocSizeOf);
+        }
+      }
+    }
+    return total;
+  }
+
+  AutoTArray<nsIFrame::ChildList,4> childListArray;
+  aFrame->GetChildLists(&childListArray);
+
+  for (nsIFrame::ChildListArrayIterator childLists(childListArray);
+       !childLists.IsDone(); childLists.Next()) {
+    for (nsFrameList::Enumerator e(childLists.CurrentList());
+         !e.AtEnd(); e.Next()) {
+      total += SizeOfTextRunsForFrames(e.get(), aMallocSizeOf, clear);
+    }
+  }
+  return total;
+}
+
+struct PrefCallbacks
+{
+  const char* name;
+  PrefChangedFunc func;
+};
+static const PrefCallbacks kPrefCallbacks[] = {
+  { GRID_ENABLED_PREF_NAME,
+    GridEnabledPrefChangeCallback },
+  { WEBKIT_PREFIXES_ENABLED_PREF_NAME,
+    WebkitPrefixEnabledPrefChangeCallback },
+  { TEXT_ALIGN_UNSAFE_ENABLED_PREF_NAME,
+    TextAlignUnsafeEnabledPrefChangeCallback },
+  { DISPLAY_CONTENTS_ENABLED_PREF_NAME,
+    DisplayContentsEnabledPrefChangeCallback },
+  { FLOAT_LOGICAL_VALUES_ENABLED_PREF_NAME,
+    FloatLogicalValuesEnabledPrefChangeCallback },
+  { BG_CLIP_TEXT_ENABLED_PREF_NAME,
+    BackgroundClipTextEnabledPrefChangeCallback },
+};
+
+/* static */
+void
+nsLayoutUtils::Initialize()
+{
+  Preferences::AddUintVarCache(&sFontSizeInflationMaxRatio,
+                               "font.size.inflation.maxRatio");
+  Preferences::AddUintVarCache(&sFontSizeInflationEmPerLine,
+                               "font.size.inflation.emPerLine");
+  Preferences::AddUintVarCache(&sFontSizeInflationMinTwips,
+                               "font.size.inflation.minTwips");
+  Preferences::AddUintVarCache(&sFontSizeInflationLineThreshold,
+                               "font.size.inflation.lineThreshold");
+  Preferences::AddIntVarCache(&sFontSizeInflationMappingIntercept,
+                              "font.size.inflation.mappingIntercept");
+  Preferences::AddBoolVarCache(&sFontSizeInflationForceEnabled,
+                               "font.size.inflation.forceEnabled");
+  Preferences::AddBoolVarCache(&sFontSizeInflationDisabledInMasterProcess,
+                               "font.size.inflation.disabledInMasterProcess");
+  Preferences::AddBoolVarCache(&sInvalidationDebuggingIsEnabled,
+                               "nglayout.debug.invalidation");
+  Preferences::AddBoolVarCache(&sCSSVariablesEnabled,
+                               "layout.css.variables.enabled");
+  Preferences::AddBoolVarCache(&sInterruptibleReflowEnabled,
+                               "layout.interruptible-reflow.enabled");
+  Preferences::AddBoolVarCache(&sSVGTransformBoxEnabled,
+                               "svg.transform-box.enabled");
+  Preferences::AddBoolVarCache(&sTextCombineUprightDigitsEnabled,
+                               "layout.css.text-combine-upright-digits.enabled");
+#ifdef MOZ_STYLO
+  Preferences::AddBoolVarCache(&sStyloEnabled,
+                               "layout.css.servo.enabled");
+#endif
+  Preferences::AddUintVarCache(&sIdlePeriodDeadlineLimit,
+                               "layout.idle_period.time_limit",
+                               DEFAULT_IDLE_PERIOD_TIME_LIMIT);
+  Preferences::AddUintVarCache(&sQuiescentFramesBeforeIdlePeriod,
+                               "layout.idle_period.required_quiescent_frames",
+                               DEFAULT_QUIESCENT_FRAMES);
+
+  for (auto& callback : kPrefCallbacks) {
+    Preferences::RegisterCallbackAndCall(callback.func, callback.name);
+  }
+  nsComputedDOMStyle::RegisterPrefChangeCallbacks();
+}
+
+/* static */
+void
+nsLayoutUtils::Shutdown()
+{
+  if (sContentMap) {
+    delete sContentMap;
+    sContentMap = nullptr;
+  }
+
+  for (auto& callback : kPrefCallbacks) {
+    Preferences::UnregisterCallback(callback.func, callback.name);
+  }
+  nsComputedDOMStyle::UnregisterPrefChangeCallbacks();
+
+  // so the cached initial quotes array doesn't appear to be a leak
+  nsStyleList::Shutdown();
+}
+
+/* static */
+void
+nsLayoutUtils::RegisterImageRequest(nsPresContext* aPresContext,
+                                    imgIRequest* aRequest,
+                                    bool* aRequestRegistered)
+{
+  if (!aPresContext) {
+    return;
+  }
+
+  if (aRequestRegistered && *aRequestRegistered) {
+    // Our request is already registered with the refresh driver, so
+    // no need to register it again.
+    return;
+  }
+
+  if (aRequest) {
+    if (!aPresContext->RefreshDriver()->AddImageRequest(aRequest)) {
+      NS_WARNING("Unable to add image request");
+      return;
+    }
+
+    if (aRequestRegistered) {
+      *aRequestRegistered = true;
+    }
+  }
+}
+
+/* static */
+void
+nsLayoutUtils::RegisterImageRequestIfAnimated(nsPresContext* aPresContext,
+                                              imgIRequest* aRequest,
+                                              bool* aRequestRegistered)
+{
+  if (!aPresContext) {
+    return;
+  }
+
+  if (aRequestRegistered && *aRequestRegistered) {
+    // Our request is already registered with the refresh driver, so
+    // no need to register it again.
+    return;
+  }
+
+  if (aRequest) {
+    nsCOMPtr<imgIContainer> image;
+    if (NS_SUCCEEDED(aRequest->GetImage(getter_AddRefs(image)))) {
+      // Check to verify that the image is animated. If so, then add it to the
+      // list of images tracked by the refresh driver.
+      bool isAnimated = false;
+      nsresult rv = image->GetAnimated(&isAnimated);
+      if (NS_SUCCEEDED(rv) && isAnimated) {
+        if (!aPresContext->RefreshDriver()->AddImageRequest(aRequest)) {
+          NS_WARNING("Unable to add image request");
+          return;
+        }
+
+        if (aRequestRegistered) {
+          *aRequestRegistered = true;
+        }
+      }
+    }
+  }
+}
+
+/* static */
+void
+nsLayoutUtils::DeregisterImageRequest(nsPresContext* aPresContext,
+                                      imgIRequest* aRequest,
+                                      bool* aRequestRegistered)
+{
+  if (!aPresContext) {
+    return;
+  }
+
+  // Deregister our imgIRequest with the refresh driver to
+  // complete tear-down, but only if it has been registered
+  if (aRequestRegistered && !*aRequestRegistered) {
+    return;
+  }
+
+  if (aRequest) {
+    nsCOMPtr<imgIContainer> image;
+    if (NS_SUCCEEDED(aRequest->GetImage(getter_AddRefs(image)))) {
+      aPresContext->RefreshDriver()->RemoveImageRequest(aRequest);
+
+      if (aRequestRegistered) {
+        *aRequestRegistered = false;
+      }
+    }
+  }
+}
+
+/* static */
+void
+nsLayoutUtils::PostRestyleEvent(Element* aElement,
+                                nsRestyleHint aRestyleHint,
+                                nsChangeHint aMinChangeHint)
+{
+  nsIDocument* doc = aElement->GetComposedDoc();
+  if (doc) {
+    nsCOMPtr<nsIPresShell> presShell = doc->GetShell();
+    if (presShell) {
+      presShell->GetPresContext()->RestyleManager()->PostRestyleEvent(
+        aElement, aRestyleHint, aMinChangeHint);
+    }
+  }
+}
+
+nsSetAttrRunnable::nsSetAttrRunnable(nsIContent* aContent, nsIAtom* aAttrName,
+                                     const nsAString& aValue)
+  : mContent(aContent),
+    mAttrName(aAttrName),
+    mValue(aValue)
+{
+  NS_ASSERTION(aContent && aAttrName, "Missing stuff, prepare to crash");
+}
+
+nsSetAttrRunnable::nsSetAttrRunnable(nsIContent* aContent, nsIAtom* aAttrName,
+                                     int32_t aValue)
+  : mContent(aContent),
+    mAttrName(aAttrName)
+{
+  NS_ASSERTION(aContent && aAttrName, "Missing stuff, prepare to crash");
+  mValue.AppendInt(aValue);
+}
+
+NS_IMETHODIMP
+nsSetAttrRunnable::Run()
+{
+  return mContent->SetAttr(kNameSpaceID_None, mAttrName, mValue, true);
+}
+
+nsUnsetAttrRunnable::nsUnsetAttrRunnable(nsIContent* aContent,
+                                         nsIAtom* aAttrName)
+  : mContent(aContent),
+    mAttrName(aAttrName)
+{
+  NS_ASSERTION(aContent && aAttrName, "Missing stuff, prepare to crash");
+}
+
+NS_IMETHODIMP
+nsUnsetAttrRunnable::Run()
+{
+  return mContent->UnsetAttr(kNameSpaceID_None, mAttrName, true);
+}
+
+/**
+ * Compute the minimum font size inside of a container with the given
+ * width, such that **when the user zooms the container to fill the full
+ * width of the device**, the fonts satisfy our minima.
+ */
+static nscoord
+MinimumFontSizeFor(nsPresContext* aPresContext, WritingMode aWritingMode,
+                   nscoord aContainerISize)
+{
+  nsIPresShell* presShell = aPresContext->PresShell();
+
+  uint32_t emPerLine = presShell->FontSizeInflationEmPerLine();
+  uint32_t minTwips = presShell->FontSizeInflationMinTwips();
+  if (emPerLine == 0 && minTwips == 0) {
+    return 0;
+  }
+
+  // Clamp the container width to the device dimensions
+  nscoord iFrameISize = aWritingMode.IsVertical()
+    ? aPresContext->GetVisibleArea().height
+    : aPresContext->GetVisibleArea().width;
+  nscoord effectiveContainerISize = std::min(iFrameISize, aContainerISize);
+
+  nscoord byLine = 0, byInch = 0;
+  if (emPerLine != 0) {
+    byLine = effectiveContainerISize / emPerLine;
+  }
+  if (minTwips != 0) {
+    // REVIEW: Is this giving us app units and sizes *not* counting
+    // viewport scaling?
+    gfxSize screenSize = aPresContext->ScreenSizeInchesForFontInflation();
+    float deviceISizeInches = aWritingMode.IsVertical()
+      ? screenSize.height : screenSize.width;
+    byInch = NSToCoordRound(effectiveContainerISize /
+                            (deviceISizeInches * 1440 /
+                             minTwips ));
+  }
+  return std::max(byLine, byInch);
+}
+
+/* static */ float
+nsLayoutUtils::FontSizeInflationInner(const nsIFrame *aFrame,
+                                      nscoord aMinFontSize)
+{
+  // Note that line heights should be inflated by the same ratio as the
+  // font size of the same text; thus we operate only on the font size
+  // even when we're scaling a line height.
+  nscoord styleFontSize = aFrame->StyleFont()->mFont.size;
+  if (styleFontSize <= 0) {
+    // Never scale zero font size.
+    return 1.0;
+  }
+
+  if (aMinFontSize <= 0) {
+    // No need to scale.
+    return 1.0;
+  }
+
+  // If between this current frame and its font inflation container there is a
+  // non-inline element with fixed width or height, then we should not inflate
+  // fonts for this frame.
+  for (const nsIFrame* f = aFrame;
+       f && !f->IsContainerForFontSizeInflation();
+       f = f->GetParent()) {
+    nsIContent* content = f->GetContent();
+    nsIAtom* fType = f->GetType();
+    nsIFrame* parent = f->GetParent();
+    // Also, if there is more than one frame corresponding to a single
+    // content node, we want the outermost one.
+    if (!(parent && parent->GetContent() == content) &&
+        // ignore width/height on inlines since they don't apply
+        fType != nsGkAtoms::inlineFrame &&
+        // ignore width on radios and checkboxes since we enlarge them and
+        // they have width/height in ua.css
+        fType != nsGkAtoms::formControlFrame) {
+      // ruby annotations should have the same inflation as its
+      // grandparent, which is the ruby frame contains the annotation.
+      if (fType == nsGkAtoms::rubyTextFrame) {
+        MOZ_ASSERT(parent &&
+                   parent->GetType() == nsGkAtoms::rubyTextContainerFrame);
+        nsIFrame* grandparent = parent->GetParent();
+        MOZ_ASSERT(grandparent &&
+                   grandparent->GetType() == nsGkAtoms::rubyFrame);
+        return FontSizeInflationFor(grandparent);
+      }
+      nsStyleCoord stylePosWidth = f->StylePosition()->mWidth;
+      nsStyleCoord stylePosHeight = f->StylePosition()->mHeight;
+      if (stylePosWidth.GetUnit() != eStyleUnit_Auto ||
+          stylePosHeight.GetUnit() != eStyleUnit_Auto) {
+
+        return 1.0;
+      }
+    }
+  }
+
+  int32_t interceptParam = nsLayoutUtils::FontSizeInflationMappingIntercept();
+  float maxRatio = (float)nsLayoutUtils::FontSizeInflationMaxRatio() / 100.0f;
+
+  float ratio = float(styleFontSize) / float(aMinFontSize);
+  float inflationRatio;
+
+  // Given a minimum inflated font size m, a specified font size s, we want to
+  // find the inflated font size i and then return the ratio of i to s (i/s).
+  if (interceptParam >= 0) {
+    // Since the mapping intercept parameter P is greater than zero, we use it
+    // to determine the point where our mapping function intersects the i=s
+    // line. This means that we have an equation of the form:
+    //
+    // i = m + s·(P/2)/(1 + P/2), if s <= (1 + P/2)·m
+    // i = s, if s >= (1 + P/2)·m
+
+    float intercept = 1 + float(interceptParam)/2.0f;
+    if (ratio >= intercept) {
+      // If we're already at 1+P/2 or more times the minimum, don't scale.
+      return 1.0;
+    }
+
+    // The point (intercept, intercept) is where the part of the i vs. s graph
+    // that's not slope 1 meets the i=s line.  (This part of the
+    // graph is a line from (0, m), to that point). We calculate the
+    // intersection point to be ((1+P/2)m, (1+P/2)m), where P is the
+    // intercept parameter above. We then need to return i/s.
+    inflationRatio = (1.0f + (ratio * (intercept - 1) / intercept)) / ratio;
+  } else {
+    // This is the case where P is negative. We essentially want to implement
+    // the case for P=infinity here, so we make i = s + m, which means that
+    // i/s = s/s + m/s = 1 + 1/ratio
+    inflationRatio = 1 + 1.0f / ratio;
+  }
+
+  if (maxRatio > 1.0 && inflationRatio > maxRatio) {
+    return maxRatio;
+  } else {
+    return inflationRatio;
+  }
+}
+
+static bool
+ShouldInflateFontsForContainer(const nsIFrame *aFrame)
+{
+  // We only want to inflate fonts for text that is in a place
+  // with room to expand.  The question is what the best heuristic for
+  // that is...
+  // For now, we're going to use NS_FRAME_IN_CONSTRAINED_BSIZE, which
+  // indicates whether the frame is inside something with a constrained
+  // block-size (propagating down the tree), but the propagation stops when
+  // we hit overflow-y [or -x, for vertical mode]: scroll or auto.
+  const nsStyleText* styleText = aFrame->StyleText();
+
+  return styleText->mTextSizeAdjust != NS_STYLE_TEXT_SIZE_ADJUST_NONE &&
+         !(aFrame->GetStateBits() & NS_FRAME_IN_CONSTRAINED_BSIZE) &&
+         // We also want to disable font inflation for containers that have
+         // preformatted text.
+         // MathML cells need special treatment. See bug 1002526 comment 56.
+         (styleText->WhiteSpaceCanWrap(aFrame) ||
+          aFrame->IsFrameOfType(nsIFrame::eMathML));
+}
+
+nscoord
+nsLayoutUtils::InflationMinFontSizeFor(const nsIFrame *aFrame)
+{
+  nsPresContext *presContext = aFrame->PresContext();
+  if (!FontSizeInflationEnabled(presContext) ||
+      presContext->mInflationDisabledForShrinkWrap) {
+    return 0;
+  }
+
+  for (const nsIFrame *f = aFrame; f; f = f->GetParent()) {
+    if (f->IsContainerForFontSizeInflation()) {
+      if (!ShouldInflateFontsForContainer(f)) {
+        return 0;
+      }
+
+      nsFontInflationData *data =
+        nsFontInflationData::FindFontInflationDataFor(aFrame);
+      // FIXME: The need to null-check here is sort of a bug, and might
+      // lead to incorrect results.
+      if (!data || !data->InflationEnabled()) {
+        return 0;
+      }
+
+      return MinimumFontSizeFor(aFrame->PresContext(),
+                                aFrame->GetWritingMode(),
+                                data->EffectiveISize());
+    }
+  }
+
+  MOZ_ASSERT(false, "root should always be container");
+
+  return 0;
+}
+
+float
+nsLayoutUtils::FontSizeInflationFor(const nsIFrame *aFrame)
+{
+  if (aFrame->IsSVGText()) {
+    const nsIFrame* container = aFrame;
+    while (container->GetType() != nsGkAtoms::svgTextFrame) {
+      container = container->GetParent();
+    }
+    NS_ASSERTION(container, "expected to find an ancestor SVGTextFrame");
+    return
+      static_cast<const SVGTextFrame*>(container)->GetFontSizeScaleFactor();
+  }
+
+  if (!FontSizeInflationEnabled(aFrame->PresContext())) {
+    return 1.0f;
+  }
+
+  return FontSizeInflationInner(aFrame, InflationMinFontSizeFor(aFrame));
+}
+
+/* static */ bool
+nsLayoutUtils::FontSizeInflationEnabled(nsPresContext *aPresContext)
+{
+  nsIPresShell* presShell = aPresContext->GetPresShell();
+
+  if (!presShell) {
+    return false;
+  }
+
+  return presShell->FontSizeInflationEnabled();
+}
+
+/* static */ nsRect
+nsLayoutUtils::GetBoxShadowRectForFrame(nsIFrame* aFrame,
+                                        const nsSize& aFrameSize)
+{
+  nsCSSShadowArray* boxShadows = aFrame->StyleEffects()->mBoxShadow;
+  if (!boxShadows) {
+    return nsRect();
+  }
+
+  bool nativeTheme;
+  const nsStyleDisplay* styleDisplay = aFrame->StyleDisplay();
+  nsITheme::Transparency transparency;
+  if (aFrame->IsThemed(styleDisplay, &transparency)) {
+    // For opaque (rectangular) theme widgets we can take the generic
+    // border-box path with border-radius disabled.
+    nativeTheme = transparency != nsITheme::eOpaque;
+  } else {
+    nativeTheme = false;
+  }
+
+  nsRect frameRect = nativeTheme ?
+    aFrame->GetVisualOverflowRectRelativeToSelf() :
+    nsRect(nsPoint(0, 0), aFrameSize);
+
+  nsRect shadows;
+  int32_t A2D = aFrame->PresContext()->AppUnitsPerDevPixel();
+  for (uint32_t i = 0; i < boxShadows->Length(); ++i) {
+    nsRect tmpRect = frameRect;
+    nsCSSShadowItem* shadow = boxShadows->ShadowAt(i);
+
+    // inset shadows are never painted outside the frame
+    if (shadow->mInset)
+      continue;
+
+    tmpRect.MoveBy(nsPoint(shadow->mXOffset, shadow->mYOffset));
+    tmpRect.Inflate(shadow->mSpread);
+    tmpRect.Inflate(
+      nsContextBoxBlur::GetBlurRadiusMargin(shadow->mRadius, A2D));
+    shadows.UnionRect(shadows, tmpRect);
+  }
+  return shadows;
+}
+
+/* static */ bool
+nsLayoutUtils::GetContentViewerSize(nsPresContext* aPresContext,
+                                    LayoutDeviceIntSize& aOutSize)
+{
+  nsCOMPtr<nsIDocShell> docShell = aPresContext->GetDocShell();
+  if (!docShell) {
+    return false;
+  }
+
+  nsCOMPtr<nsIContentViewer> cv;
+  docShell->GetContentViewer(getter_AddRefs(cv));
+  if (!cv) {
+    return false;
+  }
+
+  nsIntRect bounds;
+  cv->GetBounds(bounds);
+  aOutSize = LayoutDeviceIntRect::FromUnknownRect(bounds).Size();
+  return true;
+}
+
+static bool
+UpdateCompositionBoundsForRCDRSF(ParentLayerRect& aCompBounds,
+                                 nsPresContext* aPresContext,
+                                 bool aScaleContentViewerSize)
+{
+  nsIFrame* rootFrame = aPresContext->PresShell()->GetRootFrame();
+  if (!rootFrame) {
+    return false;
+  }
+
+#if defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
+  nsIWidget* widget = rootFrame->GetNearestWidget();
+#else
+  nsView* view = rootFrame->GetView();
+  nsIWidget* widget = view ? view->GetWidget() : nullptr;
+#endif
+
+  if (widget) {
+    LayoutDeviceIntRect widgetBounds = widget->GetBounds();
+    widgetBounds.MoveTo(0, 0);
+    aCompBounds = ParentLayerRect(
+      ViewAs<ParentLayerPixel>(
+        widgetBounds,
+        PixelCastJustification::LayoutDeviceIsParentLayerForRCDRSF));
+    return true;
+  }
+
+  LayoutDeviceIntSize contentSize;
+  if (nsLayoutUtils::GetContentViewerSize(aPresContext, contentSize)) {
+    LayoutDeviceToParentLayerScale scale;
+    if (aScaleContentViewerSize && aPresContext->GetParentPresContext()) {
+      scale = LayoutDeviceToParentLayerScale(
+        aPresContext->GetParentPresContext()->PresShell()->GetCumulativeResolution());
+    }
+    aCompBounds.SizeTo(contentSize * scale);
+    return true;
+  }
+
+  return false;
+}
+
+/* static */ nsMargin
+nsLayoutUtils::ScrollbarAreaToExcludeFromCompositionBoundsFor(nsIFrame* aScrollFrame)
+{
+  if (!aScrollFrame || !aScrollFrame->GetScrollTargetFrame()) {
+    return nsMargin();
+  }
+  nsPresContext* presContext = aScrollFrame->PresContext();
+  nsIPresShell* presShell = presContext->GetPresShell();
+  if (!presShell) {
+    return nsMargin();
+  }
+  bool isRootScrollFrame = aScrollFrame == presShell->GetRootScrollFrame();
+  bool isRootContentDocRootScrollFrame = isRootScrollFrame
+                                      && presContext->IsRootContentDocument();
+  if (!isRootContentDocRootScrollFrame) {
+    return nsMargin();
+  }
+  if (LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars)) {
+    return nsMargin();
+  }
+  nsIScrollableFrame* scrollableFrame = aScrollFrame->GetScrollTargetFrame();
+  if (!scrollableFrame) {
+    return nsMargin();
+  }
+  return scrollableFrame->GetActualScrollbarSizes();
+}
+
+/* static */ nsSize
+nsLayoutUtils::CalculateCompositionSizeForFrame(nsIFrame* aFrame, bool aSubtractScrollbars)
+{
+  // If we have a scrollable frame, restrict the composition bounds to its
+  // scroll port. The scroll port excludes the frame borders and the scroll
+  // bars, which we don't want to be part of the composition bounds.
+  nsIScrollableFrame* scrollableFrame = aFrame->GetScrollTargetFrame();
+  nsRect rect = scrollableFrame ? scrollableFrame->GetScrollPortRect() : aFrame->GetRect();
+  nsSize size = rect.Size();
+
+  nsPresContext* presContext = aFrame->PresContext();
+  nsIPresShell* presShell = presContext->PresShell();
+
+  bool isRootContentDocRootScrollFrame = presContext->IsRootContentDocument()
+                                      && aFrame == presShell->GetRootScrollFrame();
+  if (isRootContentDocRootScrollFrame) {
+    ParentLayerRect compBounds;
+    if (UpdateCompositionBoundsForRCDRSF(compBounds, presContext, false)) {
+      int32_t auPerDevPixel = presContext->AppUnitsPerDevPixel();
+      size = nsSize(compBounds.width * auPerDevPixel, compBounds.height * auPerDevPixel);
+    }
+  }
+
+  if (aSubtractScrollbars) {
+    nsMargin margins = ScrollbarAreaToExcludeFromCompositionBoundsFor(aFrame);
+    size.width -= margins.LeftRight();
+    size.height -= margins.TopBottom();
+  }
+
+  return size;
+}
+
+/* static */ CSSSize
+nsLayoutUtils::CalculateRootCompositionSize(nsIFrame* aFrame,
+                                            bool aIsRootContentDocRootScrollFrame,
+                                            const FrameMetrics& aMetrics)
+{
+
+  if (aIsRootContentDocRootScrollFrame) {
+    return ViewAs<LayerPixel>(aMetrics.GetCompositionBounds().Size(),
+                              PixelCastJustification::ParentLayerToLayerForRootComposition)
+           * LayerToScreenScale(1.0f)
+           / aMetrics.DisplayportPixelsPerCSSPixel();
+  }
+  nsPresContext* presContext = aFrame->PresContext();
+  ScreenSize rootCompositionSize;
+  nsPresContext* rootPresContext =
+    presContext->GetToplevelContentDocumentPresContext();
+  if (!rootPresContext) {
+    rootPresContext = presContext->GetRootPresContext();
+  }
+  nsIPresShell* rootPresShell = nullptr;
+  if (rootPresContext) {
+    rootPresShell = rootPresContext->PresShell();
+    if (nsIFrame* rootFrame = rootPresShell->GetRootFrame()) {
+      LayoutDeviceToLayerScale2D cumulativeResolution(
+        rootPresShell->GetCumulativeResolution()
+      * nsLayoutUtils::GetTransformToAncestorScale(rootFrame));
+      ParentLayerRect compBounds;
+      if (UpdateCompositionBoundsForRCDRSF(compBounds, rootPresContext, true)) {
+        rootCompositionSize = ViewAs<ScreenPixel>(compBounds.Size(),
+            PixelCastJustification::ScreenIsParentLayerForRoot);
+      } else {
+        int32_t rootAUPerDevPixel = rootPresContext->AppUnitsPerDevPixel();
+        LayerSize frameSize =
+          (LayoutDeviceRect::FromAppUnits(rootFrame->GetRect(), rootAUPerDevPixel)
+           * cumulativeResolution).Size();
+        rootCompositionSize = frameSize * LayerToScreenScale(1.0f);
+      }
+    }
+  } else {
+    nsIWidget* widget = aFrame->GetNearestWidget();
+    LayoutDeviceIntRect widgetBounds = widget->GetBounds();
+    rootCompositionSize = ScreenSize(
+      ViewAs<ScreenPixel>(widgetBounds.Size(),
+                          PixelCastJustification::LayoutDeviceIsScreenForBounds));
+  }
+
+  // Adjust composition size for the size of scroll bars.
+  nsIFrame* rootRootScrollFrame = rootPresShell ? rootPresShell->GetRootScrollFrame() : nullptr;
+  nsMargin scrollbarMargins = ScrollbarAreaToExcludeFromCompositionBoundsFor(rootRootScrollFrame);
+  LayoutDeviceMargin margins = LayoutDeviceMargin::FromAppUnits(scrollbarMargins,
+    rootPresContext->AppUnitsPerDevPixel());
+  // Scrollbars are not subject to resolution scaling, so LD pixels = layer pixels for them.
+  rootCompositionSize.width -= margins.LeftRight();
+  rootCompositionSize.height -= margins.TopBottom();
+
+  return rootCompositionSize / aMetrics.DisplayportPixelsPerCSSPixel();
+}
+
+/* static */ nsRect
+nsLayoutUtils::CalculateScrollableRectForFrame(nsIScrollableFrame* aScrollableFrame, nsIFrame* aRootFrame)
+{
+  nsRect contentBounds;
+  if (aScrollableFrame) {
+    contentBounds = aScrollableFrame->GetScrollRange();
+
+    nsPoint scrollPosition = aScrollableFrame->GetScrollPosition();
+    if (aScrollableFrame->GetScrollbarStyles().mVertical == NS_STYLE_OVERFLOW_HIDDEN) {
+      contentBounds.y = scrollPosition.y;
+      contentBounds.height = 0;
+    }
+    if (aScrollableFrame->GetScrollbarStyles().mHorizontal == NS_STYLE_OVERFLOW_HIDDEN) {
+      contentBounds.x = scrollPosition.x;
+      contentBounds.width = 0;
+    }
+
+    contentBounds.width += aScrollableFrame->GetScrollPortRect().width;
+    contentBounds.height += aScrollableFrame->GetScrollPortRect().height;
+  } else {
+    contentBounds = aRootFrame->GetRect();
+  }
+  return contentBounds;
+}
+
+/* static */ nsRect
+nsLayoutUtils::CalculateExpandedScrollableRect(nsIFrame* aFrame)
+{
+  nsRect scrollableRect =
+    CalculateScrollableRectForFrame(aFrame->GetScrollTargetFrame(),
+                                    aFrame->PresContext()->PresShell()->GetRootFrame());
+  nsSize compSize = CalculateCompositionSizeForFrame(aFrame);
+
+  if (aFrame == aFrame->PresContext()->PresShell()->GetRootScrollFrame()) {
+    // the composition size for the root scroll frame does not include the
+    // local resolution, so we adjust.
+    float res = aFrame->PresContext()->PresShell()->GetResolution();
+    compSize.width = NSToCoordRound(compSize.width / res);
+    compSize.height = NSToCoordRound(compSize.height / res);
+  }
+
+  if (scrollableRect.width < compSize.width) {
+    scrollableRect.x = std::max(0,
+                                scrollableRect.x - (compSize.width - scrollableRect.width));
+    scrollableRect.width = compSize.width;
+  }
+
+  if (scrollableRect.height < compSize.height) {
+    scrollableRect.y = std::max(0,
+                                scrollableRect.y - (compSize.height - scrollableRect.height));
+    scrollableRect.height = compSize.height;
+  }
+  return scrollableRect;
+}
+
+/* static */ void
+nsLayoutUtils::DoLogTestDataForPaint(LayerManager* aManager,
+                                     ViewID aScrollId,
+                                     const std::string& aKey,
+                                     const std::string& aValue)
+{
+  if (ClientLayerManager* mgr = aManager->AsClientLayerManager()) {
+    mgr->LogTestDataForCurrentPaint(aScrollId, aKey, aValue);
+  }
+}
+
+/* static */ bool
+nsLayoutUtils::IsAPZTestLoggingEnabled()
+{
+  return gfxPrefs::APZTestLoggingEnabled();
+}
+
+////////////////////////////////////////
+// SurfaceFromElementResult
+
+nsLayoutUtils::SurfaceFromElementResult::SurfaceFromElementResult()
+  // Use safe default values here
+  : mIsWriteOnly(true)
+  , mIsStillLoading(false)
+  , mHasSize(false)
+  , mCORSUsed(false)
+  , mIsPremultiplied(true)
+{
+}
+
+const RefPtr<mozilla::gfx::SourceSurface>&
+nsLayoutUtils::SurfaceFromElementResult::GetSourceSurface()
+{
+  if (!mSourceSurface && mLayersImage) {
+    mSourceSurface = mLayersImage->GetAsSourceSurface();
+  }
+
+  return mSourceSurface;
+}
+
+////////////////////////////////////////
+
+bool
+nsLayoutUtils::IsNonWrapperBlock(nsIFrame* aFrame)
+{
+  return GetAsBlock(aFrame) && !aFrame->IsBlockWrapper();
+}
+
+bool
+nsLayoutUtils::NeedsPrintPreviewBackground(nsPresContext* aPresContext)
+{
+  return aPresContext->IsRootPaginatedDocument() &&
+    (aPresContext->Type() == nsPresContext::eContext_PrintPreview ||
+     aPresContext->Type() == nsPresContext::eContext_PageLayout);
+}
+
+AutoMaybeDisableFontInflation::AutoMaybeDisableFontInflation(nsIFrame *aFrame)
+{
+  // FIXME: Now that inflation calculations are based on the flow
+  // root's NCA's (nearest common ancestor of its inflatable
+  // descendants) width, we could probably disable inflation in
+  // fewer cases than we currently do.
+  // MathML cells need special treatment. See bug 1002526 comment 56.
+  if (aFrame->IsContainerForFontSizeInflation() &&
+      !aFrame->IsFrameOfType(nsIFrame::eMathML)) {
+    mPresContext = aFrame->PresContext();
+    mOldValue = mPresContext->mInflationDisabledForShrinkWrap;
+    mPresContext->mInflationDisabledForShrinkWrap = true;
+  } else {
+    // indicate we have nothing to restore
+    mPresContext = nullptr;
+  }
+}
+
+AutoMaybeDisableFontInflation::~AutoMaybeDisableFontInflation()
+{
+  if (mPresContext) {
+    mPresContext->mInflationDisabledForShrinkWrap = mOldValue;
+  }
+}
+
+namespace mozilla {
+
+Rect NSRectToRect(const nsRect& aRect, double aAppUnitsPerPixel)
+{
+  // Note that by making aAppUnitsPerPixel a double we're doing floating-point
+  // division using a larger type and avoiding rounding error.
+  return Rect(Float(aRect.x / aAppUnitsPerPixel),
+              Float(aRect.y / aAppUnitsPerPixel),
+              Float(aRect.width / aAppUnitsPerPixel),
+              Float(aRect.height / aAppUnitsPerPixel));
+}
+
+Rect NSRectToSnappedRect(const nsRect& aRect, double aAppUnitsPerPixel,
+                         const gfx::DrawTarget& aSnapDT)
+{
+  // Note that by making aAppUnitsPerPixel a double we're doing floating-point
+  // division using a larger type and avoiding rounding error.
+  Rect rect(Float(aRect.x / aAppUnitsPerPixel),
+            Float(aRect.y / aAppUnitsPerPixel),
+            Float(aRect.width / aAppUnitsPerPixel),
+            Float(aRect.height / aAppUnitsPerPixel));
+  MaybeSnapToDevicePixels(rect, aSnapDT, true);
+  return rect;
+}
+// Similar to a snapped rect, except an axis is left unsnapped if the snapping
+// process results in a length of 0.
+Rect NSRectToNonEmptySnappedRect(const nsRect& aRect, double aAppUnitsPerPixel,
+                                 const gfx::DrawTarget& aSnapDT)
+{
+  // Note that by making aAppUnitsPerPixel a double we're doing floating-point
+  // division using a larger type and avoiding rounding error.
+  Rect rect(Float(aRect.x / aAppUnitsPerPixel),
+            Float(aRect.y / aAppUnitsPerPixel),
+            Float(aRect.width / aAppUnitsPerPixel),
+            Float(aRect.height / aAppUnitsPerPixel));
+  MaybeSnapToDevicePixels(rect, aSnapDT, true, false);
+  return rect;
+}
+
+void StrokeLineWithSnapping(const nsPoint& aP1, const nsPoint& aP2,
+                            int32_t aAppUnitsPerDevPixel,
+                            DrawTarget& aDrawTarget,
+                            const Pattern& aPattern,
+                            const StrokeOptions& aStrokeOptions,
+                            const DrawOptions& aDrawOptions)
+{
+  Point p1 = NSPointToPoint(aP1, aAppUnitsPerDevPixel);
+  Point p2 = NSPointToPoint(aP2, aAppUnitsPerDevPixel);
+  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget,
+                                    aStrokeOptions.mLineWidth);
+  aDrawTarget.StrokeLine(p1, p2, aPattern, aStrokeOptions, aDrawOptions);
+}
+
+namespace layout {
+
+
+void
+MaybeSetupTransactionIdAllocator(layers::LayerManager* aManager, nsView* aView)
+{
+  if (aManager->GetBackendType() == layers::LayersBackend::LAYERS_CLIENT) {
+    layers::ClientLayerManager *manager = static_cast<layers::ClientLayerManager*>(aManager);
+    nsRefreshDriver *refresh = aView->GetViewManager()->GetPresShell()->GetPresContext()->RefreshDriver();
+    manager->SetTransactionIdAllocator(refresh);
+  }
+}
+
+} // namespace layout
+} // namespace mozilla
+
+/* static */ bool
+nsLayoutUtils::IsOutlineStyleAutoEnabled()
+{
+  static bool sOutlineStyleAutoEnabled;
+  static bool sOutlineStyleAutoPrefCached = false;
+
+  if (!sOutlineStyleAutoPrefCached) {
+    sOutlineStyleAutoPrefCached = true;
+    Preferences::AddBoolVarCache(&sOutlineStyleAutoEnabled,
+                                 "layout.css.outline-style-auto.enabled",
+                                 false);
+  }
+  return sOutlineStyleAutoEnabled;
+}
+
+/* static */ void
+nsLayoutUtils::SetBSizeFromFontMetrics(const nsIFrame* aFrame,
+                                       ReflowOutput& aMetrics,
+                                       const LogicalMargin& aFramePadding,
+                                       WritingMode aLineWM,
+                                       WritingMode aFrameWM)
+{
+  RefPtr<nsFontMetrics> fm =
+    nsLayoutUtils::GetInflatedFontMetricsForFrame(aFrame);
+
+  if (fm) {
+    // Compute final height of the frame.
+    //
+    // Do things the standard css2 way -- though it's hard to find it
+    // in the css2 spec! It's actually found in the css1 spec section
+    // 4.4 (you will have to read between the lines to really see
+    // it).
+    //
+    // The height of our box is the sum of our font size plus the top
+    // and bottom border and padding. The height of children do not
+    // affect our height.
+    aMetrics.SetBlockStartAscent(aLineWM.IsLineInverted() ? fm->MaxDescent()
+                                                          : fm->MaxAscent());
+    aMetrics.BSize(aLineWM) = fm->MaxHeight();
+  } else {
+    NS_WARNING("Cannot get font metrics - defaulting sizes to 0");
+    aMetrics.SetBlockStartAscent(aMetrics.BSize(aLineWM) = 0);
+  }
+  aMetrics.SetBlockStartAscent(aMetrics.BlockStartAscent() +
+                               aFramePadding.BStart(aFrameWM));
+  aMetrics.BSize(aLineWM) += aFramePadding.BStartEnd(aFrameWM);
+}
+
+/* static */ bool
+nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(nsIPresShell* aShell)
+{
+  if (nsIDocument* doc = aShell->GetDocument()) {
+    WidgetEvent event(true, eVoidEvent);
+    nsTArray<EventTarget*> targets;
+    nsresult rv = EventDispatcher::Dispatch(doc, nullptr, &event, nullptr,
+        nullptr, nullptr, &targets);
+    NS_ENSURE_SUCCESS(rv, false);
+    for (size_t i = 0; i < targets.Length(); i++) {
+      if (targets[i]->IsApzAware()) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+static void
+MaybeReflowForInflationScreenSizeChange(nsPresContext *aPresContext)
+{
+  if (aPresContext) {
+    nsIPresShell* presShell = aPresContext->GetPresShell();
+    bool fontInflationWasEnabled = presShell->FontSizeInflationEnabled();
+    presShell->NotifyFontSizeInflationEnabledIsDirty();
+    bool changed = false;
+    if (presShell && presShell->FontSizeInflationEnabled() &&
+        presShell->FontSizeInflationMinTwips() != 0) {
+      aPresContext->ScreenSizeInchesForFontInflation(&changed);
+    }
+
+    changed = changed ||
+      (fontInflationWasEnabled != presShell->FontSizeInflationEnabled());
+    if (changed) {
+      nsCOMPtr<nsIDocShell> docShell = aPresContext->GetDocShell();
+      if (docShell) {
+        nsCOMPtr<nsIContentViewer> cv;
+        docShell->GetContentViewer(getter_AddRefs(cv));
+        if (cv) {
+          nsTArray<nsCOMPtr<nsIContentViewer> > array;
+          cv->AppendSubtree(array);
+          for (uint32_t i = 0, iEnd = array.Length(); i < iEnd; ++i) {
+            nsCOMPtr<nsIPresShell> shell;
+            nsCOMPtr<nsIContentViewer> cv = array[i];
+            cv->GetPresShell(getter_AddRefs(shell));
+            if (shell) {
+              nsIFrame *rootFrame = shell->GetRootFrame();
+              if (rootFrame) {
+                shell->FrameNeedsReflow(rootFrame,
+                                        nsIPresShell::eStyleChange,
+                                        NS_FRAME_IS_DIRTY);
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
+
+/* static */ void
+nsLayoutUtils::SetScrollPositionClampingScrollPortSize(nsIPresShell* aPresShell, CSSSize aSize)
+{
+  MOZ_ASSERT(aSize.width >= 0.0 && aSize.height >= 0.0);
+
+  aPresShell->SetScrollPositionClampingScrollPortSize(
+    nsPresContext::CSSPixelsToAppUnits(aSize.width),
+    nsPresContext::CSSPixelsToAppUnits(aSize.height));
+
+  // When the "font.size.inflation.minTwips" preference is set, the
+  // layout depends on the size of the screen.  Since when the size
+  // of the screen changes, the scroll position clamping scroll port
+  // size also changes, we hook in the needed updates here rather
+  // than adding a separate notification just for this change.
+  nsPresContext* presContext = aPresShell->GetPresContext();
+  MaybeReflowForInflationScreenSizeChange(presContext);
+}
+
+/* static */ bool
+nsLayoutUtils::CanScrollOriginClobberApz(nsIAtom* aScrollOrigin)
+{
+  return aScrollOrigin != nullptr
+      && aScrollOrigin != nsGkAtoms::apz
+      && aScrollOrigin != nsGkAtoms::restore;
+}
+
+/* static */ ScrollMetadata
+nsLayoutUtils::ComputeScrollMetadata(nsIFrame* aForFrame,
+                                     nsIFrame* aScrollFrame,
+                                     nsIContent* aContent,
+                                     const nsIFrame* aReferenceFrame,
+                                     Layer* aLayer,
+                                     ViewID aScrollParentId,
+                                     const nsRect& aViewport,
+                                     const Maybe<nsRect>& aClipRect,
+                                     bool aIsRootContent,
+                                     const ContainerLayerParameters& aContainerParameters)
+{
+  nsPresContext* presContext = aForFrame->PresContext();
+  int32_t auPerDevPixel = presContext->AppUnitsPerDevPixel();
+
+  nsIPresShell* presShell = presContext->GetPresShell();
+  ScrollMetadata metadata;
+  FrameMetrics& metrics = metadata.GetMetrics();
+  metrics.SetViewport(CSSRect::FromAppUnits(aViewport));
+
+  ViewID scrollId = FrameMetrics::NULL_SCROLL_ID;
+  if (aContent) {
+    if (void* paintRequestTime = aContent->GetProperty(nsGkAtoms::paintRequestTime)) {
+      metrics.SetPaintRequestTime(*static_cast<TimeStamp*>(paintRequestTime));
+      aContent->DeleteProperty(nsGkAtoms::paintRequestTime);
+    }
+    scrollId = nsLayoutUtils::FindOrCreateIDFor(aContent);
+    nsRect dp;
+    if (nsLayoutUtils::GetDisplayPort(aContent, &dp)) {
+      metrics.SetDisplayPort(CSSRect::FromAppUnits(dp));
+      nsLayoutUtils::LogTestDataForPaint(aLayer->Manager(), scrollId, "displayport",
+          metrics.GetDisplayPort());
+    }
+    if (nsLayoutUtils::GetCriticalDisplayPort(aContent, &dp)) {
+      metrics.SetCriticalDisplayPort(CSSRect::FromAppUnits(dp));
+      nsLayoutUtils::LogTestDataForPaint(aLayer->Manager(), scrollId,
+          "criticalDisplayport", metrics.GetCriticalDisplayPort());
+    }
+    DisplayPortMarginsPropertyData* marginsData =
+        static_cast<DisplayPortMarginsPropertyData*>(aContent->GetProperty(nsGkAtoms::DisplayPortMargins));
+    if (marginsData) {
+      metrics.SetDisplayPortMargins(marginsData->mMargins);
+    }
+  }
+
+  nsIScrollableFrame* scrollableFrame = nullptr;
+  if (aScrollFrame)
+    scrollableFrame = aScrollFrame->GetScrollTargetFrame();
+
+  metrics.SetScrollableRect(CSSRect::FromAppUnits(
+    nsLayoutUtils::CalculateScrollableRectForFrame(scrollableFrame, aForFrame)));
+
+  if (scrollableFrame) {
+    nsPoint scrollPosition = scrollableFrame->GetScrollPosition();
+    metrics.SetScrollOffset(CSSPoint::FromAppUnits(scrollPosition));
+
+    nsPoint smoothScrollPosition = scrollableFrame->LastScrollDestination();
+    metrics.SetSmoothScrollOffset(CSSPoint::FromAppUnits(smoothScrollPosition));
+
+    // If the frame was scrolled since the last layers update, and by something
+    // that is higher priority than APZ, we want to tell the APZ to update
+    // its scroll offset. We want to distinguish the case where the scroll offset
+    // was "restored" because in that case the restored scroll position should
+    // not overwrite a user-driven scroll.
+    if (scrollableFrame->LastScrollOrigin() == nsGkAtoms::restore) {
+      metrics.SetScrollOffsetRestored(scrollableFrame->CurrentScrollGeneration());
+    } else if (CanScrollOriginClobberApz(scrollableFrame->LastScrollOrigin())) {
+      metrics.SetScrollOffsetUpdated(scrollableFrame->CurrentScrollGeneration());
+    }
+    scrollableFrame->AllowScrollOriginDowngrade();
+
+    nsIAtom* lastSmoothScrollOrigin = scrollableFrame->LastSmoothScrollOrigin();
+    if (lastSmoothScrollOrigin) {
+      metrics.SetSmoothScrollOffsetUpdated(scrollableFrame->CurrentScrollGeneration());
+    }
+
+    nsSize lineScrollAmount = scrollableFrame->GetLineScrollAmount();
+    LayoutDeviceIntSize lineScrollAmountInDevPixels =
+      LayoutDeviceIntSize::FromAppUnitsRounded(lineScrollAmount, presContext->AppUnitsPerDevPixel());
+    metadata.SetLineScrollAmount(lineScrollAmountInDevPixels);
+
+    nsSize pageScrollAmount = scrollableFrame->GetPageScrollAmount();
+    LayoutDeviceIntSize pageScrollAmountInDevPixels =
+      LayoutDeviceIntSize::FromAppUnitsRounded(pageScrollAmount, presContext->AppUnitsPerDevPixel());
+    metadata.SetPageScrollAmount(pageScrollAmountInDevPixels);
+
+    if (!aScrollFrame->GetParent() ||
+        EventStateManager::CanVerticallyScrollFrameWithWheel(aScrollFrame->GetParent()))
+    {
+      metadata.SetAllowVerticalScrollWithWheel(true);
+    }
+
+    metadata.SetUsesContainerScrolling(scrollableFrame->UsesContainerScrolling());
+
+    metadata.SetSnapInfo(scrollableFrame->GetScrollSnapInfo());
+  }
+
+  // If we have the scrollparent being the same as the scroll id, the
+  // compositor-side code could get into an infinite loop while building the
+  // overscroll handoff chain.
+  MOZ_ASSERT(aScrollParentId == FrameMetrics::NULL_SCROLL_ID || scrollId != aScrollParentId);
+  metrics.SetScrollId(scrollId);
+  metrics.SetIsRootContent(aIsRootContent);
+  metadata.SetScrollParentId(aScrollParentId);
+
+  if (scrollId != FrameMetrics::NULL_SCROLL_ID && !presContext->GetParentPresContext()) {
+    if ((aScrollFrame && (aScrollFrame == presShell->GetRootScrollFrame())) ||
+        aContent == presShell->GetDocument()->GetDocumentElement()) {
+      metadata.SetIsLayersIdRoot(true);
+    }
+  }
+
+  // Only the root scrollable frame for a given presShell should pick up
+  // the presShell's resolution. All the other frames are 1.0.
+  if (aScrollFrame == presShell->GetRootScrollFrame()) {
+    metrics.SetPresShellResolution(presShell->GetResolution());
+  } else {
+    metrics.SetPresShellResolution(1.0f);
+  }
+  // The cumulative resolution is the resolution at which the scroll frame's
+  // content is actually rendered. It includes the pres shell resolutions of
+  // all the pres shells from here up to the root, as well as any css-driven
+  // resolution. We don't need to compute it as it's already stored in the
+  // container parameters.
+  metrics.SetCumulativeResolution(aContainerParameters.Scale());
+
+  LayoutDeviceToScreenScale2D resolutionToScreen(
+      presShell->GetCumulativeResolution()
+    * nsLayoutUtils::GetTransformToAncestorScale(aScrollFrame ? aScrollFrame : aForFrame));
+  metrics.SetExtraResolution(metrics.GetCumulativeResolution() / resolutionToScreen);
+
+  metrics.SetDevPixelsPerCSSPixel(presContext->CSSToDevPixelScale());
+
+  // Initially, AsyncPanZoomController should render the content to the screen
+  // at the painted resolution.
+  const LayerToParentLayerScale layerToParentLayerScale(1.0f);
+  metrics.SetZoom(metrics.GetCumulativeResolution() * metrics.GetDevPixelsPerCSSPixel()
+                  * layerToParentLayerScale);
+
+  // Calculate the composition bounds as the size of the scroll frame and
+  // its origin relative to the reference frame.
+  // If aScrollFrame is null, we are in a document without a root scroll frame,
+  // so it's a xul document. In this case, use the size of the viewport frame.
+  nsIFrame* frameForCompositionBoundsCalculation = aScrollFrame ? aScrollFrame : aForFrame;
+  nsRect compositionBounds(frameForCompositionBoundsCalculation->GetOffsetToCrossDoc(aReferenceFrame),
+                           frameForCompositionBoundsCalculation->GetSize());
+  if (scrollableFrame) {
+    // If we have a scrollable frame, restrict the composition bounds to its
+    // scroll port. The scroll port excludes the frame borders and the scroll
+    // bars, which we don't want to be part of the composition bounds.
+    nsRect scrollPort = scrollableFrame->GetScrollPortRect();
+    compositionBounds = nsRect(compositionBounds.TopLeft() + scrollPort.TopLeft(),
+                               scrollPort.Size());
+  }
+  ParentLayerRect frameBounds = LayoutDeviceRect::FromAppUnits(compositionBounds, auPerDevPixel)
+                              * metrics.GetCumulativeResolution()
+                              * layerToParentLayerScale;
+
+  if (aClipRect) {
+    ParentLayerRect rect = LayoutDeviceRect::FromAppUnits(*aClipRect, auPerDevPixel)
+                         * metrics.GetCumulativeResolution()
+                         * layerToParentLayerScale;
+    metadata.SetScrollClip(Some(LayerClip(RoundedToInt(rect))));
+  }
+
+  // For the root scroll frame of the root content document (RCD-RSF), the above calculation
+  // will yield the size of the viewport frame as the composition bounds, which
+  // doesn't actually correspond to what is visible when
+  // nsIDOMWindowUtils::setCSSViewport has been called to modify the visible area of
+  // the prescontext that the viewport frame is reflowed into. In that case if our
+  // document has a widget then the widget's bounds will correspond to what is
+  // visible. If we don't have a widget the root view's bounds correspond to what
+  // would be visible because they don't get modified by setCSSViewport.
+  bool isRootScrollFrame = aScrollFrame == presShell->GetRootScrollFrame();
+  bool isRootContentDocRootScrollFrame = isRootScrollFrame
+                                      && presContext->IsRootContentDocument();
+  if (isRootContentDocRootScrollFrame) {
+    UpdateCompositionBoundsForRCDRSF(frameBounds, presContext, true);
+  }
+
+  nsMargin sizes = ScrollbarAreaToExcludeFromCompositionBoundsFor(aScrollFrame);
+  // Scrollbars are not subject to resolution scaling, so LD pixels = layer pixels for them.
+  ParentLayerMargin boundMargins = LayoutDeviceMargin::FromAppUnits(sizes, auPerDevPixel)
+    * LayoutDeviceToParentLayerScale(1.0f);
+  frameBounds.Deflate(boundMargins);
+
+  metrics.SetCompositionBounds(frameBounds);
+
+  metrics.SetRootCompositionSize(
+    nsLayoutUtils::CalculateRootCompositionSize(aScrollFrame ? aScrollFrame : aForFrame,
+                                                isRootContentDocRootScrollFrame, metrics));
+
+  if (gfxPrefs::APZPrintTree() || gfxPrefs::APZTestLoggingEnabled()) {
+    if (nsIContent* content = frameForCompositionBoundsCalculation->GetContent()) {
+      nsAutoString contentDescription;
+      content->Describe(contentDescription);
+      metadata.SetContentDescription(NS_LossyConvertUTF16toASCII(contentDescription));
+      nsLayoutUtils::LogTestDataForPaint(aLayer->Manager(), scrollId, "contentDescription",
+          metadata.GetContentDescription().get());
+    }
+  }
+
+  metrics.SetPresShellId(presShell->GetPresShellId());
+
+  // If the scroll frame's content is marked 'scrollgrab', record this
+  // in the FrameMetrics so APZ knows to provide the scroll grabbing
+  // behaviour.
+  if (aScrollFrame && nsContentUtils::HasScrollgrab(aScrollFrame->GetContent())) {
+    metadata.SetHasScrollgrab(true);
+  }
+
+  // Also compute and set the background color.
+  // This is needed for APZ overscrolling support.
+  if (aScrollFrame) {
+    if (isRootScrollFrame) {
+      metadata.SetBackgroundColor(Color::FromABGR(
+        presShell->GetCanvasBackground()));
+    } else {
+      nsStyleContext* backgroundStyle;
+      if (nsCSSRendering::FindBackground(aScrollFrame, &backgroundStyle)) {
+        metadata.SetBackgroundColor(Color::FromABGR(
+          backgroundStyle->StyleBackground()->mBackgroundColor));
+      }
+    }
+  }
+
+  if (ShouldDisableApzForElement(aContent)) {
+    metadata.SetForceDisableApz(true);
+  }
+
+  return metadata;
+}
+
+/* static */ bool
+nsLayoutUtils::ContainsMetricsWithId(const Layer* aLayer, const ViewID& aScrollId)
+{
+  for (uint32_t i = aLayer->GetScrollMetadataCount(); i > 0; i--) {
+    if (aLayer->GetFrameMetrics(i-1).GetScrollId() == aScrollId) {
+      return true;
+    }
+  }
+  for (Layer* child = aLayer->GetFirstChild(); child; child = child->GetNextSibling()) {
+    if (ContainsMetricsWithId(child, aScrollId)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/* static */ uint32_t
+nsLayoutUtils::GetTouchActionFromFrame(nsIFrame* aFrame)
+{
+  // If aFrame is null then return default value
+  if (!aFrame) {
+    return NS_STYLE_TOUCH_ACTION_AUTO;
+  }
+
+  // The touch-action CSS property applies to: all elements except:
+  // non-replaced inline elements, table rows, row groups, table columns, and column groups
+  bool isNonReplacedInlineElement = aFrame->IsFrameOfType(nsIFrame::eLineParticipant);
+  if (isNonReplacedInlineElement) {
+    return NS_STYLE_TOUCH_ACTION_AUTO;
+  }
+
+  const nsStyleDisplay* disp = aFrame->StyleDisplay();
+  bool isTableElement = disp->IsInnerTableStyle() &&
+    disp->mDisplay != StyleDisplay::TableCell &&
+    disp->mDisplay != StyleDisplay::TableCaption;
+  if (isTableElement) {
+    return NS_STYLE_TOUCH_ACTION_AUTO;
+  }
+
+  return disp->mTouchAction;
+}
+
+/* static */  void
+nsLayoutUtils::TransformToAncestorAndCombineRegions(
+  const nsRegion& aRegion,
+  nsIFrame* aFrame,
+  const nsIFrame* aAncestorFrame,
+  nsRegion* aPreciseTargetDest,
+  nsRegion* aImpreciseTargetDest,
+  Maybe<Matrix4x4>* aMatrixCache)
+{
+  if (aRegion.IsEmpty()) {
+    return;
+  }
+  bool isPrecise;
+  RegionBuilder<nsRegion> transformedRegion;
+  for (nsRegion::RectIterator it = aRegion.RectIter(); !it.Done(); it.Next()) {
+    nsRect transformed = TransformFrameRectToAncestor(
+      aFrame, it.Get(), aAncestorFrame, &isPrecise, aMatrixCache);
+    transformedRegion.OrWith(transformed);
+  }
+  nsRegion* dest = isPrecise ? aPreciseTargetDest : aImpreciseTargetDest;
+  dest->OrWith(transformedRegion.ToRegion());
+}
+
+/* static */ bool
+nsLayoutUtils::ShouldUseNoScriptSheet(nsIDocument* aDocument)
+{
+  // also handle the case where print is done from print preview
+  // see bug #342439 for more details
+  if (aDocument->IsStaticDocument()) {
+    aDocument = aDocument->GetOriginalDocument();
+  }
+  return aDocument->IsScriptEnabled();
+}
+
+/* static */ bool
+nsLayoutUtils::ShouldUseNoFramesSheet(nsIDocument* aDocument)
+{
+  bool allowSubframes = true;
+  nsIDocShell* docShell = aDocument->GetDocShell();
+  if (docShell) {
+    docShell->GetAllowSubframes(&allowSubframes);
+  }
+  return !allowSubframes;
+}
+
+/* static */ void
+nsLayoutUtils::GetFrameTextContent(nsIFrame* aFrame, nsAString& aResult)
+{
+  aResult.Truncate();
+  AppendFrameTextContent(aFrame, aResult);
+}
+
+/* static */ void
+nsLayoutUtils::AppendFrameTextContent(nsIFrame* aFrame, nsAString& aResult)
+{
+  if (aFrame->GetType() == nsGkAtoms::textFrame) {
+    auto textFrame = static_cast<nsTextFrame*>(aFrame);
+    auto offset = textFrame->GetContentOffset();
+    auto length = textFrame->GetContentLength();
+    textFrame->GetContent()->
+      GetText()->AppendTo(aResult, offset, length);
+  } else {
+    for (nsIFrame* child : aFrame->PrincipalChildList()) {
+      AppendFrameTextContent(child, aResult);
+    }
+  }
+}
+
+/* static */
+nsRect
+nsLayoutUtils::GetSelectionBoundingRect(Selection* aSel)
+{
+  nsRect res;
+  // Bounding client rect may be empty after calling GetBoundingClientRect
+  // when range is collapsed. So we get caret's rect when range is
+  // collapsed.
+  if (aSel->IsCollapsed()) {
+    nsIFrame* frame = nsCaret::GetGeometry(aSel, &res);
+    if (frame) {
+      nsIFrame* relativeTo = GetContainingBlockForClientRect(frame);
+      res = TransformFrameRectToAncestor(frame, res, relativeTo);
+    }
+  } else {
+    int32_t rangeCount = aSel->RangeCount();
+    RectAccumulator accumulator;
+    for (int32_t idx = 0; idx < rangeCount; ++idx) {
+      nsRange* range = aSel->GetRangeAt(idx);
+      nsRange::CollectClientRectsAndText(&accumulator, nullptr, range,
+                                  range->GetStartParent(), range->StartOffset(),
+                                  range->GetEndParent(), range->EndOffset(),
+                                  true, false);
+    }
+    res = accumulator.mResultRect.IsEmpty() ? accumulator.mFirstRect :
+      accumulator.mResultRect;
+  }
+
+  return res;
+}
+
+/* static */ nsBlockFrame*
+nsLayoutUtils::GetFloatContainingBlock(nsIFrame* aFrame)
+{
+  nsIFrame* ancestor = aFrame->GetParent();
+  while (ancestor && !ancestor->IsFloatContainingBlock()) {
+    ancestor = ancestor->GetParent();
+  }
+  MOZ_ASSERT(!ancestor || GetAsBlock(ancestor),
+             "Float containing block can only be block frame");
+  return static_cast<nsBlockFrame*>(ancestor);
+}
+
+// The implementation of this calculation is adapted from
+// Element::GetBoundingClientRect().
+/* static */ CSSRect
+nsLayoutUtils::GetBoundingContentRect(const nsIContent* aContent,
+                                      const nsIScrollableFrame* aRootScrollFrame) {
+  CSSRect result;
+  if (nsIFrame* frame = aContent->GetPrimaryFrame()) {
+    nsIFrame* relativeTo = aRootScrollFrame->GetScrolledFrame();
+    result = CSSRect::FromAppUnits(
+        nsLayoutUtils::GetAllInFlowRectsUnion(
+            frame,
+            relativeTo,
+            nsLayoutUtils::RECTS_ACCOUNT_FOR_TRANSFORMS));
+
+    // If the element is contained in a scrollable frame that is not
+    // the root scroll frame, make sure to clip the result so that it is
+    // not larger than the containing scrollable frame's bounds.
+    nsIScrollableFrame* scrollFrame = nsLayoutUtils::GetNearestScrollableFrame(frame);
+    if (scrollFrame && scrollFrame != aRootScrollFrame) {
+      nsIFrame* subFrame = do_QueryFrame(scrollFrame);
+      MOZ_ASSERT(subFrame);
+      // Get the bounds of the scroll frame in the same coordinate space
+      // as |result|.
+      CSSRect subFrameRect = CSSRect::FromAppUnits(
+          nsLayoutUtils::TransformFrameRectToAncestor(
+              subFrame,
+              subFrame->GetRectRelativeToSelf(),
+              relativeTo));
+
+      result = subFrameRect.Intersect(result);
+    }
+  }
+  return result;
+}
+
+static already_AddRefed<nsIPresShell>
+GetPresShell(const nsIContent* aContent)
+{
+  nsCOMPtr<nsIPresShell> result;
+  if (nsIDocument* doc = aContent->GetComposedDoc()) {
+    result = doc->GetShell();
+  }
+  return result.forget();
+}
+
+static void UpdateDisplayPortMarginsForPendingMetrics(FrameMetrics& aMetrics) {
+  nsIContent* content = nsLayoutUtils::FindContentFor(aMetrics.GetScrollId());
+  if (!content) {
+    return;
+  }
+
+  nsCOMPtr<nsIPresShell> shell = GetPresShell(content);
+  if (!shell) {
+    return;
+  }
+
+  MOZ_ASSERT(aMetrics.GetUseDisplayPortMargins());
+
+  if (gfxPrefs::APZAllowZooming() && aMetrics.IsRootContent()) {
+    // See APZCCallbackHelper::UpdateRootFrame for details.
+    float presShellResolution = shell->GetResolution();
+    if (presShellResolution != aMetrics.GetPresShellResolution()) {
+      return;
+    }
+  }
+
+  nsIScrollableFrame* frame = nsLayoutUtils::FindScrollableFrameFor(aMetrics.GetScrollId());
+
+  if (!frame) {
+    return;
+  }
+
+  if (APZCCallbackHelper::IsScrollInProgress(frame)) {
+    // If these conditions are true, then the UpdateFrame
+    // message may be ignored by the main-thread, so we
+    // shouldn't update the displayport based on it.
+    return;
+  }
+
+  DisplayPortMarginsPropertyData* currentData =
+    static_cast<DisplayPortMarginsPropertyData*>(content->GetProperty(nsGkAtoms::DisplayPortMargins));
+  if (!currentData) {
+    return;
+  }
+
+  CSSPoint frameScrollOffset = CSSPoint::FromAppUnits(frame->GetScrollPosition());
+  APZCCallbackHelper::AdjustDisplayPortForScrollDelta(aMetrics, frameScrollOffset);
+
+  nsLayoutUtils::SetDisplayPortMargins(content, shell,
+                                       aMetrics.GetDisplayPortMargins(), 0);
+}
+
+/* static */ void
+nsLayoutUtils::UpdateDisplayPortMarginsFromPendingMessages()
+{
+  if (mozilla::dom::ContentChild::GetSingleton() &&
+      mozilla::dom::ContentChild::GetSingleton()->GetIPCChannel()) {
+    CompositorBridgeChild::Get()->GetIPCChannel()->PeekMessages(
+      [](const IPC::Message& aMsg) -> bool {
+        if (aMsg.type() == mozilla::layers::PAPZ::Msg_RequestContentRepaint__ID) {
+          PickleIterator iter(aMsg);
+          FrameMetrics frame;
+          if (!IPC::ReadParam(&aMsg, &iter, &frame)) {
+            MOZ_ASSERT(false);
+            return true;
+          }
+
+          UpdateDisplayPortMarginsForPendingMetrics(frame);
+        }
+        return true;
+      });
+  }
+}
+
+/* static */ bool
+nsLayoutUtils::IsTransformed(nsIFrame* aForFrame, nsIFrame* aTopFrame)
+{
+  for (nsIFrame* f = aForFrame; f != aTopFrame; f = f->GetParent()) {
+    if (f->IsTransformed()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/*static*/ CSSPoint
+nsLayoutUtils::GetCumulativeApzCallbackTransform(nsIFrame* aFrame)
+{
+  CSSPoint delta;
+  if (!aFrame) {
+    return delta;
+  }
+  nsIFrame* frame = aFrame;
+  nsCOMPtr<nsIContent> content = frame->GetContent();
+  nsCOMPtr<nsIContent> lastContent;
+  while (frame) {
+    if (content && (content != lastContent)) {
+      void* property = content->GetProperty(nsGkAtoms::apzCallbackTransform);
+      if (property) {
+        delta += *static_cast<CSSPoint*>(property);
+      }
+    }
+    frame = GetCrossDocParentFrame(frame);
+    lastContent = content;
+    content = frame ? frame->GetContent() : nullptr;
+  }
+  return delta;
+}
+
+/* static */ bool
+nsLayoutUtils::SupportsServoStyleBackend(nsIDocument* aDocument)
+{
+  return StyloEnabled() &&
+         aDocument->IsHTMLOrXHTML() &&
+         static_cast<nsDocument*>(aDocument)->IsContentDocument();
+}
+
+static
+bool
+LineHasNonEmptyContentWorker(nsIFrame* aFrame)
+{
+  // Look for non-empty frames, but ignore inline and br frames.
+  // For inline frames, descend into the children, if any.
+  if (aFrame->GetType() == nsGkAtoms::inlineFrame) {
+    for (nsIFrame* child : aFrame->PrincipalChildList()) {
+      if (LineHasNonEmptyContentWorker(child)) {
+        return true;
+      }
+    }
+  } else {
+    if (aFrame->GetType() != nsGkAtoms::brFrame &&
+        !aFrame->IsEmpty()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+static
+bool
+LineHasNonEmptyContent(nsLineBox* aLine)
+{
+  int32_t count = aLine->GetChildCount();
+  for (nsIFrame* frame = aLine->mFirstChild; count > 0;
+       --count, frame = frame->GetNextSibling()) {
+    if (LineHasNonEmptyContentWorker(frame)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/* static */ bool
+nsLayoutUtils::IsInvisibleBreak(nsINode* aNode, nsIFrame** aNextLineFrame)
+{
+  if (aNextLineFrame) {
+    *aNextLineFrame = nullptr;
+  }
+
+  if (!aNode->IsElement() || !aNode->IsEditable()) {
+    return false;
+  }
+  nsIFrame* frame = aNode->AsElement()->GetPrimaryFrame();
+  if (!frame || frame->GetType() != nsGkAtoms::brFrame) {
+    return false;
+  }
+
+  nsContainerFrame* f = frame->GetParent();
+  while (f && f->IsFrameOfType(nsBox::eLineParticipant)) {
+    f = f->GetParent();
+  }
+  nsBlockFrame* blockAncestor = do_QueryFrame(f);
+  if (!blockAncestor) {
+    // The container frame doesn't support line breaking.
+    return false;
+  }
+
+  bool valid = false;
+  nsBlockInFlowLineIterator iter(blockAncestor, frame, &valid);
+  if (!valid) {
+    return false;
+  }
+
+  bool lineNonEmpty = LineHasNonEmptyContent(iter.GetLine());
+  if (!lineNonEmpty) {
+    return false;
+  }
+
+  while (iter.Next()) {
+    auto currentLine = iter.GetLine();
+    // Completely skip empty lines.
+    if (!currentLine->IsEmpty()) {
+      // If we come across an inline line, the BR has caused a visible line break.
+      if (currentLine->IsInline()) {
+        if (aNextLineFrame) {
+          *aNextLineFrame = currentLine->mFirstChild;
+        }
+        return false;
+      }
+      break;
+    }
+  }
+
+  return lineNonEmpty;
+}