Add m-esr52 at 52.6.0

1 files changed, 3159 insertions, 0 deletions

diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
new file mode 100644
index 000000000..b27e6d0e3
--- /dev/null
+++ b/layout/base/nsPresContext.cpp
@@ -0,0 +1,3159 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/* a presentation of a document, part 1 */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/EventStateManager.h"
+
+#include "base/basictypes.h"
+
+#include "nsCOMPtr.h"
+#include "nsPresContext.h"
+#include "nsIPresShell.h"
+#include "nsDocShell.h"
+#include "nsIContentViewer.h"
+#include "nsPIDOMWindow.h"
+#include "mozilla/StyleSetHandle.h"
+#include "mozilla/StyleSetHandleInlines.h"
+#include "nsIContent.h"
+#include "nsIFrame.h"
+#include "nsIDocument.h"
+#include "nsIPrintSettings.h"
+#include "nsILanguageAtomService.h"
+#include "mozilla/LookAndFeel.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIDOMHTMLDocument.h"
+#include "nsIDOMHTMLElement.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsThreadUtils.h"
+#include "nsFrameManager.h"
+#include "nsLayoutUtils.h"
+#include "nsViewManager.h"
+#include "mozilla/RestyleManager.h"
+#include "mozilla/RestyleManagerHandle.h"
+#include "mozilla/RestyleManagerHandleInlines.h"
+#include "SurfaceCacheUtils.h"
+#include "nsCSSRuleProcessor.h"
+#include "nsRuleNode.h"
+#include "gfxPlatform.h"
+#include "nsCSSRules.h"
+#include "nsFontFaceLoader.h"
+#include "mozilla/EffectCompositor.h"
+#include "mozilla/EventListenerManager.h"
+#include "prenv.h"
+#include "nsPluginFrame.h"
+#include "nsTransitionManager.h"
+#include "nsAnimationManager.h"
+#include "CounterStyleManager.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/Element.h"
+#include "nsIMessageManager.h"
+#include "mozilla/dom/MediaQueryList.h"
+#include "nsSMILAnimationController.h"
+#include "mozilla/css/ImageLoader.h"
+#include "mozilla/dom/PBrowserParent.h"
+#include "mozilla/dom/TabChild.h"
+#include "mozilla/dom/TabParent.h"
+#include "nsRefreshDriver.h"
+#include "Layers.h"
+#include "LayerUserData.h"
+#include "ClientLayerManager.h"
+#include "mozilla/dom/NotifyPaintEvent.h"
+#include "gfxPrefs.h"
+#include "nsIDOMChromeWindow.h"
+#include "nsFrameLoader.h"
+#include "mozilla/dom/FontFaceSet.h"
+#include "nsContentUtils.h"
+#include "nsPIWindowRoot.h"
+#include "mozilla/Preferences.h"
+#include "gfxTextRun.h"
+#include "nsFontFaceUtils.h"
+#include "nsLayoutStylesheetCache.h"
+#include "mozilla/StyleSheet.h"
+#include "mozilla/StyleSheetInlines.h"
+
+#if defined(MOZ_WIDGET_GTK)
+#include "gfxPlatformGtk.h" // xxx - for UseFcFontList
+#endif
+
+
+// Needed for Start/Stop of Image Animation
+#include "imgIContainer.h"
+#include "nsIImageLoadingContent.h"
+
+#include "nsCSSParser.h"
+#include "nsBidiUtils.h"
+#include "nsServiceManagerUtils.h"
+
+#include "mozilla/dom/URL.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::layers;
+
+uint8_t gNotifySubDocInvalidationData;
+
+/**
+ * Layer UserData for ContainerLayers that want to be notified
+ * of local invalidations of them and their descendant layers.
+ * Pass a callback to ComputeDifferences to have these called.
+ */
+class ContainerLayerPresContext : public LayerUserData {
+public:
+  nsPresContext* mPresContext;
+};
+
+namespace {
+
+class CharSetChangingRunnable : public Runnable
+{
+public:
+  CharSetChangingRunnable(nsPresContext* aPresContext,
+                          const nsCString& aCharSet)
+    : mPresContext(aPresContext),
+      mCharSet(aCharSet)
+  {
+  }
+
+  NS_IMETHOD Run() override
+  {
+    mPresContext->DoChangeCharSet(mCharSet);
+    return NS_OK;
+  }
+
+private:
+  RefPtr<nsPresContext> mPresContext;
+  nsCString mCharSet;
+};
+
+} // namespace
+
+nscolor
+nsPresContext::MakeColorPref(const nsString& aColor)
+{
+  nsCSSParser parser;
+  nsCSSValue value;
+  if (!parser.ParseColorString(aColor, nullptr, 0, value)) {
+    // Any better choices?
+    return NS_RGB(0, 0, 0);
+  }
+
+  nscolor color;
+  return nsRuleNode::ComputeColor(value, this, nullptr, color)
+    ? color
+    : NS_RGB(0, 0, 0);
+}
+
+bool
+nsPresContext::IsDOMPaintEventPending()
+{
+  if (mFireAfterPaintEvents) {
+    return true;
+  }
+  nsRootPresContext* drpc = GetRootPresContext();
+  if (drpc && drpc->mRefreshDriver->ViewManagerFlushIsPending()) {
+    // Since we're promising that there will be a MozAfterPaint event
+    // fired, we record an empty invalidation in case display list
+    // invalidation doesn't invalidate anything further.
+    NotifyInvalidation(nsRect(0, 0, 0, 0), 0);
+    NS_ASSERTION(mFireAfterPaintEvents, "Why aren't we planning to fire the event?");
+    return true;
+  }
+  return false;
+}
+
+void
+nsPresContext::PrefChangedCallback(const char* aPrefName, void* instance_data)
+{
+  RefPtr<nsPresContext>  presContext =
+    static_cast<nsPresContext*>(instance_data);
+
+  NS_ASSERTION(nullptr != presContext, "bad instance data");
+  if (nullptr != presContext) {
+    presContext->PreferenceChanged(aPrefName);
+  }
+}
+
+void
+nsPresContext::PrefChangedUpdateTimerCallback(nsITimer *aTimer, void *aClosure)
+{
+  nsPresContext*  presContext = (nsPresContext*)aClosure;
+  NS_ASSERTION(presContext != nullptr, "bad instance data");
+  if (presContext)
+    presContext->UpdateAfterPreferencesChanged();
+}
+
+static bool
+IsVisualCharset(const nsCString& aCharset)
+{
+  if (aCharset.LowerCaseEqualsLiteral("ibm862")             // Hebrew
+      || aCharset.LowerCaseEqualsLiteral("iso-8859-8") ) {  // Hebrew
+    return true; // visual text type
+  }
+  else {
+    return false; // logical text type
+  }
+}
+
+  // NOTE! nsPresContext::operator new() zeroes out all members, so don't
+  // bother initializing members to 0.
+
+nsPresContext::nsPresContext(nsIDocument* aDocument, nsPresContextType aType)
+  : mType(aType), mDocument(aDocument), mBaseMinFontSize(0),
+    mTextZoom(1.0), mFullZoom(1.0), mOverrideDPPX(0.0),
+    mLastFontInflationScreenSize(gfxSize(-1.0, -1.0)),
+    mPageSize(-1, -1), mPPScale(1.0f),
+    mViewportStyleScrollbar(NS_STYLE_OVERFLOW_AUTO, NS_STYLE_OVERFLOW_AUTO),
+    mImageAnimationModePref(imgIContainer::kNormalAnimMode),
+    mAllInvalidated(false),
+    mPaintFlashing(false), mPaintFlashingInitialized(false)
+{
+  // NOTE! nsPresContext::operator new() zeroes out all members, so don't
+  // bother initializing members to 0.
+
+  mDoScaledTwips = true;
+
+  SetBackgroundImageDraw(true);		// always draw the background
+  SetBackgroundColorDraw(true);
+
+  mBackgroundColor = NS_RGB(0xFF, 0xFF, 0xFF);
+
+  mUseDocumentColors = true;
+  mUseDocumentFonts = true;
+
+  // the minimum font-size is unconstrained by default
+
+  mLinkColor = NS_RGB(0x00, 0x00, 0xEE);
+  mActiveLinkColor = NS_RGB(0xEE, 0x00, 0x00);
+  mVisitedLinkColor = NS_RGB(0x55, 0x1A, 0x8B);
+  mUnderlineLinks = true;
+  mSendAfterPaintToContent = false;
+
+  mFocusTextColor = mDefaultColor;
+  mFocusBackgroundColor = mBackgroundColor;
+  mFocusRingWidth = 1;
+
+  mBodyTextColor = mDefaultColor;
+
+  if (aType == eContext_Galley) {
+    mMedium = nsGkAtoms::screen;
+  } else {
+    mMedium = nsGkAtoms::print;
+    mPaginated = true;
+  }
+  mMediaEmulated = mMedium;
+
+  if (!IsDynamic()) {
+    mImageAnimationMode = imgIContainer::kDontAnimMode;
+    mNeverAnimate = true;
+  } else {
+    mImageAnimationMode = imgIContainer::kNormalAnimMode;
+    mNeverAnimate = false;
+  }
+  NS_ASSERTION(mDocument, "Null document");
+
+  mCounterStylesDirty = true;
+
+  // if text perf logging enabled, init stats struct
+  if (MOZ_LOG_TEST(gfxPlatform::GetLog(eGfxLog_textperf), LogLevel::Warning)) {
+    mTextPerf = new gfxTextPerfMetrics();
+  }
+
+  if (Preferences::GetBool(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+    mMissingFonts = new gfxMissingFontRecorder();
+  }
+}
+
+void
+nsPresContext::Destroy()
+{
+  if (mEventManager) {
+    // unclear if these are needed, but can't hurt
+    mEventManager->NotifyDestroyPresContext(this);
+    mEventManager->SetPresContext(nullptr);
+    mEventManager = nullptr;
+  }
+
+  if (mPrefChangedTimer)
+  {
+    mPrefChangedTimer->Cancel();
+    mPrefChangedTimer = nullptr;
+  }
+
+  // Unregister preference callbacks
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "font.",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "browser.display.",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "browser.underline_anchors",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "browser.anchor_color",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "browser.active_color",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "browser.visited_color",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "image.animation_mode",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "bidi.",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "dom.send_after_paint_to_content",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "gfx.font_rendering.",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "layout.css.dpi",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "layout.css.devPixelsPerPx",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "nglayout.debug.paint_flashing",
+                                  this);
+  Preferences::UnregisterCallback(nsPresContext::PrefChangedCallback,
+                                  "nglayout.debug.paint_flashing_chrome",
+                                  this);
+
+  mRefreshDriver = nullptr;
+}
+
+nsPresContext::~nsPresContext()
+{
+  NS_PRECONDITION(!mShell, "Presshell forgot to clear our mShell pointer");
+  DetachShell();
+
+  Destroy();
+}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsPresContext)
+   NS_INTERFACE_MAP_ENTRY(nsISupports)
+   NS_INTERFACE_MAP_ENTRY(nsIObserver)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsPresContext)
+NS_IMPL_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE(nsPresContext, LastRelease())
+
+void
+nsPresContext::LastRelease()
+{
+  if (IsRoot()) {
+    static_cast<nsRootPresContext*>(this)->CancelDidPaintTimer();
+  }
+  if (mMissingFonts) {
+    mMissingFonts->Clear();
+  }
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsPresContext)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsPresContext)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAnimationManager);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocument);
+  // NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(mDeviceContext); // not xpcom
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEffectCompositor);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEventManager);
+  // NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(mLanguage); // an atom
+
+  // NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mTheme); // a service
+  // NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mLangService); // a service
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPrintSettings);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPrefChangedTimer);
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsPresContext)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mAnimationManager);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocument);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDeviceContext); // worth bothering?
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mEffectCompositor);
+  // NS_RELEASE(tmp->mLanguage); // an atom
+  // NS_IMPL_CYCLE_COLLECTION_UNLINK(mTheme); // a service
+  // NS_IMPL_CYCLE_COLLECTION_UNLINK(mLangService); // a service
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mPrintSettings);
+
+  tmp->Destroy();
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+// whether no native theme service exists;
+// if this gets set to true, we'll stop asking for it.
+static bool sNoTheme = false;
+
+// Set to true when LookAndFeelChanged needs to be called.  This is used
+// because the look and feel is a service, so there's no need to notify it from
+// more than one prescontext.
+static bool sLookAndFeelChanged;
+
+// Set to true when ThemeChanged needs to be called on mTheme.  This is used
+// because mTheme is a service, so there's no need to notify it from more than
+// one prescontext.
+static bool sThemeChanged;
+
+void
+nsPresContext::GetDocumentColorPreferences()
+{
+  // Make sure the preferences are initialized.  In the normal run,
+  // they would already be, because gfxPlatform would have been created,
+  // but in some reference tests, that is not the case.
+  gfxPrefs::GetSingleton();
+
+  int32_t useAccessibilityTheme = 0;
+  bool usePrefColors = true;
+  bool isChromeDocShell = false;
+  static int32_t sDocumentColorsSetting;
+  static bool sDocumentColorsSettingPrefCached = false;
+  if (!sDocumentColorsSettingPrefCached) {
+    sDocumentColorsSettingPrefCached = true;
+    Preferences::AddIntVarCache(&sDocumentColorsSetting,
+                                "browser.display.document_color_use",
+                                0);
+  }
+
+  nsIDocument* doc = mDocument->GetDisplayDocument();
+  if (doc && doc->GetDocShell()) {
+    isChromeDocShell = nsIDocShellTreeItem::typeChrome ==
+                       doc->GetDocShell()->ItemType();
+  } else {
+    nsCOMPtr<nsIDocShellTreeItem> docShell(mContainer);
+    if (docShell) {
+      isChromeDocShell = nsIDocShellTreeItem::typeChrome == docShell->ItemType();
+    }
+  }
+
+  mIsChromeOriginImage = mDocument->IsBeingUsedAsImage() &&
+                         IsChromeURI(mDocument->GetDocumentURI());
+
+  if (isChromeDocShell || mIsChromeOriginImage) {
+    usePrefColors = false;
+  } else {
+    useAccessibilityTheme =
+      LookAndFeel::GetInt(LookAndFeel::eIntID_UseAccessibilityTheme, 0);
+    usePrefColors = !useAccessibilityTheme;
+  }
+  if (usePrefColors) {
+    usePrefColors =
+      !Preferences::GetBool("browser.display.use_system_colors", false);
+  }
+
+  if (usePrefColors) {
+    nsAdoptingString colorStr =
+      Preferences::GetString("browser.display.foreground_color");
+
+    if (!colorStr.IsEmpty()) {
+      mDefaultColor = MakeColorPref(colorStr);
+    }
+
+    colorStr = Preferences::GetString("browser.display.background_color");
+
+    if (!colorStr.IsEmpty()) {
+      mBackgroundColor = MakeColorPref(colorStr);
+    }
+  }
+  else {
+    mDefaultColor =
+      LookAndFeel::GetColor(LookAndFeel::eColorID_WindowForeground,
+                            NS_RGB(0x00, 0x00, 0x00));
+    mBackgroundColor =
+      LookAndFeel::GetColor(LookAndFeel::eColorID_WindowBackground,
+                            NS_RGB(0xFF, 0xFF, 0xFF));
+  }
+
+  // Wherever we got the default background color from, ensure it is
+  // opaque.
+  mBackgroundColor = NS_ComposeColors(NS_RGB(0xFF, 0xFF, 0xFF),
+                                      mBackgroundColor);
+
+
+  // Now deal with the pref:
+  // 0 = default: always, except in high contrast mode
+  // 1 = always
+  // 2 = never
+  if (sDocumentColorsSetting == 1 || mDocument->IsBeingUsedAsImage()) {
+    mUseDocumentColors = true;
+  } else if (sDocumentColorsSetting == 2) {
+    mUseDocumentColors = isChromeDocShell || mIsChromeOriginImage;
+  } else {
+    MOZ_ASSERT(!useAccessibilityTheme ||
+               !(isChromeDocShell || mIsChromeOriginImage),
+               "The accessibility theme should only be on for non-chrome");
+    mUseDocumentColors = !useAccessibilityTheme;
+  }
+}
+
+void
+nsPresContext::GetUserPreferences()
+{
+  if (!GetPresShell()) {
+    // No presshell means nothing to do here.  We'll do this when we
+    // get a presshell.
+    return;
+  }
+
+  mAutoQualityMinFontSizePixelsPref =
+    Preferences::GetInt("browser.display.auto_quality_min_font_size");
+
+  // * document colors
+  GetDocumentColorPreferences();
+
+  mSendAfterPaintToContent =
+    Preferences::GetBool("dom.send_after_paint_to_content",
+                         mSendAfterPaintToContent);
+
+  // * link colors
+  mUnderlineLinks =
+    Preferences::GetBool("browser.underline_anchors", mUnderlineLinks);
+
+  nsAdoptingString colorStr = Preferences::GetString("browser.anchor_color");
+
+  if (!colorStr.IsEmpty()) {
+    mLinkColor = MakeColorPref(colorStr);
+  }
+
+  colorStr = Preferences::GetString("browser.active_color");
+
+  if (!colorStr.IsEmpty()) {
+    mActiveLinkColor = MakeColorPref(colorStr);
+  }
+
+  colorStr = Preferences::GetString("browser.visited_color");
+
+  if (!colorStr.IsEmpty()) {
+    mVisitedLinkColor = MakeColorPref(colorStr);
+  }
+
+  mUseFocusColors =
+    Preferences::GetBool("browser.display.use_focus_colors", mUseFocusColors);
+
+  mFocusTextColor = mDefaultColor;
+  mFocusBackgroundColor = mBackgroundColor;
+
+  colorStr = Preferences::GetString("browser.display.focus_text_color");
+
+  if (!colorStr.IsEmpty()) {
+    mFocusTextColor = MakeColorPref(colorStr);
+  }
+
+  colorStr = Preferences::GetString("browser.display.focus_background_color");
+
+  if (!colorStr.IsEmpty()) {
+    mFocusBackgroundColor = MakeColorPref(colorStr);
+  }
+
+  mFocusRingWidth =
+    Preferences::GetInt("browser.display.focus_ring_width", mFocusRingWidth);
+
+  mFocusRingOnAnything =
+    Preferences::GetBool("browser.display.focus_ring_on_anything",
+                         mFocusRingOnAnything);
+
+  mFocusRingStyle =
+    Preferences::GetInt("browser.display.focus_ring_style", mFocusRingStyle);
+
+  mBodyTextColor = mDefaultColor;
+
+  // * use fonts?
+  mUseDocumentFonts =
+    Preferences::GetInt("browser.display.use_document_fonts") != 0;
+
+  mPrefScrollbarSide = Preferences::GetInt("layout.scrollbar.side");
+
+  mLangGroupFontPrefs.Reset();
+  StaticPresData::Get()->ResetCachedFontPrefs();
+
+  // * image animation
+  const nsAdoptingCString& animatePref =
+    Preferences::GetCString("image.animation_mode");
+  if (animatePref.EqualsLiteral("normal"))
+    mImageAnimationModePref = imgIContainer::kNormalAnimMode;
+  else if (animatePref.EqualsLiteral("none"))
+    mImageAnimationModePref = imgIContainer::kDontAnimMode;
+  else if (animatePref.EqualsLiteral("once"))
+    mImageAnimationModePref = imgIContainer::kLoopOnceAnimMode;
+  else // dynamic change to invalid value should act like it does initially
+    mImageAnimationModePref = imgIContainer::kNormalAnimMode;
+
+  uint32_t bidiOptions = GetBidi();
+
+  int32_t prefInt =
+    Preferences::GetInt(IBMBIDI_TEXTDIRECTION_STR,
+                        GET_BIDI_OPTION_DIRECTION(bidiOptions));
+  SET_BIDI_OPTION_DIRECTION(bidiOptions, prefInt);
+  mPrefBidiDirection = prefInt;
+
+  prefInt =
+    Preferences::GetInt(IBMBIDI_TEXTTYPE_STR,
+                        GET_BIDI_OPTION_TEXTTYPE(bidiOptions));
+  SET_BIDI_OPTION_TEXTTYPE(bidiOptions, prefInt);
+
+  prefInt =
+    Preferences::GetInt(IBMBIDI_NUMERAL_STR,
+                        GET_BIDI_OPTION_NUMERAL(bidiOptions));
+  SET_BIDI_OPTION_NUMERAL(bidiOptions, prefInt);
+
+  // We don't need to force reflow: either we are initializing a new
+  // prescontext or we are being called from UpdateAfterPreferencesChanged()
+  // which triggers a reflow anyway.
+  SetBidi(bidiOptions, false);
+}
+
+void
+nsPresContext::InvalidatePaintedLayers()
+{
+  if (!mShell)
+    return;
+  nsIFrame* rootFrame = mShell->FrameManager()->GetRootFrame();
+  if (rootFrame) {
+    // FrameLayerBuilder caches invalidation-related values that depend on the
+    // appunits-per-dev-pixel ratio, so ensure that all PaintedLayer drawing
+    // is completely flushed.
+    rootFrame->InvalidateFrameSubtree();
+  }
+}
+
+void
+nsPresContext::AppUnitsPerDevPixelChanged()
+{
+  InvalidatePaintedLayers();
+
+  if (mDeviceContext) {
+    mDeviceContext->FlushFontCache();
+  }
+
+  if (HasCachedStyleData()) {
+    // All cached style data must be recomputed.
+    MediaFeatureValuesChanged(eRestyle_ForceDescendants, NS_STYLE_HINT_REFLOW);
+  }
+
+  mCurAppUnitsPerDevPixel = AppUnitsPerDevPixel();
+}
+
+void
+nsPresContext::PreferenceChanged(const char* aPrefName)
+{
+  nsDependentCString prefName(aPrefName);
+  if (prefName.EqualsLiteral("layout.css.dpi") ||
+      prefName.EqualsLiteral("layout.css.devPixelsPerPx")) {
+    int32_t oldAppUnitsPerDevPixel = AppUnitsPerDevPixel();
+    if (mDeviceContext->CheckDPIChange() && mShell) {
+      nsCOMPtr<nsIPresShell> shell = mShell;
+      // Re-fetch the view manager's window dimensions in case there's a deferred
+      // resize which hasn't affected our mVisibleArea yet
+      nscoord oldWidthAppUnits, oldHeightAppUnits;
+      RefPtr<nsViewManager> vm = shell->GetViewManager();
+      if (!vm) {
+        return;
+      }
+      vm->GetWindowDimensions(&oldWidthAppUnits, &oldHeightAppUnits);
+      float oldWidthDevPixels = oldWidthAppUnits/oldAppUnitsPerDevPixel;
+      float oldHeightDevPixels = oldHeightAppUnits/oldAppUnitsPerDevPixel;
+
+      nscoord width = NSToCoordRound(oldWidthDevPixels*AppUnitsPerDevPixel());
+      nscoord height = NSToCoordRound(oldHeightDevPixels*AppUnitsPerDevPixel());
+      vm->SetWindowDimensions(width, height);
+
+      AppUnitsPerDevPixelChanged();
+    }
+    return;
+  }
+  if (prefName.EqualsLiteral(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+    if (Preferences::GetBool(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+      if (!mMissingFonts) {
+        mMissingFonts = new gfxMissingFontRecorder();
+        // trigger reflow to detect missing fonts on the current page
+        mPrefChangePendingNeedsReflow = true;
+      }
+    } else {
+      if (mMissingFonts) {
+        mMissingFonts->Clear();
+      }
+      mMissingFonts = nullptr;
+    }
+  }
+  if (StringBeginsWith(prefName, NS_LITERAL_CSTRING("font."))) {
+    // Changes to font family preferences don't change anything in the
+    // computed style data, so the style system won't generate a reflow
+    // hint for us.  We need to do that manually.
+
+    // FIXME We could probably also handle changes to
+    // browser.display.auto_quality_min_font_size here, but that
+    // probably also requires clearing the text run cache, so don't
+    // bother (yet, anyway).
+    mPrefChangePendingNeedsReflow = true;
+  }
+  if (StringBeginsWith(prefName, NS_LITERAL_CSTRING("bidi."))) {
+    // Changes to bidi prefs need to trigger a reflow (see bug 443629)
+    mPrefChangePendingNeedsReflow = true;
+
+    // Changes to bidi.numeral also needs to empty the text run cache.
+    // This is handled in gfxTextRunWordCache.cpp.
+  }
+  if (StringBeginsWith(prefName, NS_LITERAL_CSTRING("gfx.font_rendering."))) {
+    // Changes to font_rendering prefs need to trigger a reflow
+    mPrefChangePendingNeedsReflow = true;
+  }
+  // we use a zero-delay timer to coalesce multiple pref updates
+  if (!mPrefChangedTimer)
+  {
+    // We will end up calling InvalidatePreferenceSheets one from each pres
+    // context, but all it's doing is clearing its cached sheet pointers,
+    // so it won't be wastefully recreating the sheet multiple times.
+    // The first pres context that has its mPrefChangedTimer called will
+    // be the one to cause the reconstruction of the pref style sheet.
+    nsLayoutStylesheetCache::InvalidatePreferenceSheets();
+    mPrefChangedTimer = CreateTimer(PrefChangedUpdateTimerCallback, 0);
+    if (!mPrefChangedTimer) {
+      return;
+    }
+  }
+  if (prefName.EqualsLiteral("nglayout.debug.paint_flashing") ||
+      prefName.EqualsLiteral("nglayout.debug.paint_flashing_chrome")) {
+    mPaintFlashingInitialized = false;
+    return;
+  }
+}
+
+void
+nsPresContext::UpdateAfterPreferencesChanged()
+{
+  mPrefChangedTimer = nullptr;
+
+  if (!mContainer) {
+    // Delay updating until there is a container
+    mNeedsPrefUpdate = true;
+    return;
+  }
+
+  nsCOMPtr<nsIDocShellTreeItem> docShell(mContainer);
+  if (docShell && nsIDocShellTreeItem::typeChrome == docShell->ItemType()) {
+    return;
+  }
+
+  // Initialize our state from the user preferences
+  GetUserPreferences();
+
+  // update the presShell: tell it to set the preference style rules up
+  if (mShell) {
+    mShell->UpdatePreferenceStyles();
+  }
+
+  InvalidatePaintedLayers();
+  mDeviceContext->FlushFontCache();
+
+  nsChangeHint hint = nsChangeHint(0);
+
+  if (mPrefChangePendingNeedsReflow) {
+    hint |= NS_STYLE_HINT_REFLOW;
+  }
+
+  // Preferences require rerunning selector matching because we rebuild
+  // the pref style sheet for some preference changes.
+  RebuildAllStyleData(hint, eRestyle_Subtree);
+}
+
+nsresult
+nsPresContext::Init(nsDeviceContext* aDeviceContext)
+{
+  NS_ASSERTION(!mInitialized, "attempt to reinit pres context");
+  NS_ENSURE_ARG(aDeviceContext);
+
+  mDeviceContext = aDeviceContext;
+
+  if (mDeviceContext->SetFullZoom(mFullZoom))
+    mDeviceContext->FlushFontCache();
+  mCurAppUnitsPerDevPixel = AppUnitsPerDevPixel();
+
+  mEventManager = new mozilla::EventStateManager();
+
+  mEffectCompositor = new mozilla::EffectCompositor(this);
+  mTransitionManager = new nsTransitionManager(this);
+  mAnimationManager = new nsAnimationManager(this);
+
+  if (mDocument->GetDisplayDocument()) {
+    NS_ASSERTION(mDocument->GetDisplayDocument()->GetShell() &&
+                 mDocument->GetDisplayDocument()->GetShell()->GetPresContext(),
+                 "Why are we being initialized?");
+    mRefreshDriver = mDocument->GetDisplayDocument()->GetShell()->
+      GetPresContext()->RefreshDriver();
+  } else {
+    nsIDocument* parent = mDocument->GetParentDocument();
+    // Unfortunately, sometimes |parent| here has no presshell because
+    // printing screws up things.  Assert that in other cases it does,
+    // but whenever the shell is null just fall back on using our own
+    // refresh driver.
+    NS_ASSERTION(!parent || mDocument->IsStaticDocument() || parent->GetShell(),
+                 "How did we end up with a presshell if our parent doesn't "
+                 "have one?");
+    if (parent && parent->GetShell()) {
+      NS_ASSERTION(parent->GetShell()->GetPresContext(),
+                   "How did we get a presshell?");
+
+      // We don't have our container set yet at this point
+      nsCOMPtr<nsIDocShellTreeItem> ourItem = mDocument->GetDocShell();
+      if (ourItem) {
+        nsCOMPtr<nsIDocShellTreeItem> parentItem;
+        ourItem->GetSameTypeParent(getter_AddRefs(parentItem));
+        if (parentItem) {
+          Element* containingElement =
+            parent->FindContentForSubDocument(mDocument);
+          if (!containingElement->IsXULElement() ||
+              !containingElement->
+                HasAttr(kNameSpaceID_None,
+                        nsGkAtoms::forceOwnRefreshDriver)) {
+            mRefreshDriver = parent->GetShell()->GetPresContext()->RefreshDriver();
+          }
+        }
+      }
+    }
+
+    if (!mRefreshDriver) {
+      mRefreshDriver = new nsRefreshDriver(this);
+    }
+  }
+
+  mLangService = do_GetService(NS_LANGUAGEATOMSERVICE_CONTRACTID);
+
+  // Register callbacks so we're notified when the preferences change
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "font.",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "browser.display.",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "browser.underline_anchors",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "browser.anchor_color",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "browser.active_color",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "browser.visited_color",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "image.animation_mode",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "bidi.",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "dom.send_after_paint_to_content",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "gfx.font_rendering.",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "layout.css.dpi",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "layout.css.devPixelsPerPx",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "nglayout.debug.paint_flashing",
+                                this);
+  Preferences::RegisterCallback(nsPresContext::PrefChangedCallback,
+                                "nglayout.debug.paint_flashing_chrome",
+                                this);
+
+  nsresult rv = mEventManager->Init();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mEventManager->SetPresContext(this);
+
+#ifdef RESTYLE_LOGGING
+  mRestyleLoggingEnabled = RestyleManager::RestyleLoggingInitiallyEnabled();
+#endif
+
+#ifdef DEBUG
+  mInitialized = true;
+#endif
+
+  mBorderWidthTable[NS_STYLE_BORDER_WIDTH_THIN] = CSSPixelsToAppUnits(1);
+  mBorderWidthTable[NS_STYLE_BORDER_WIDTH_MEDIUM] = CSSPixelsToAppUnits(3);
+  mBorderWidthTable[NS_STYLE_BORDER_WIDTH_THICK] = CSSPixelsToAppUnits(5);
+
+  return NS_OK;
+}
+
+// Note: We don't hold a reference on the shell; it has a reference to
+// us
+void
+nsPresContext::AttachShell(nsIPresShell* aShell, StyleBackendType aBackendType)
+{
+  MOZ_ASSERT(!mShell);
+  mShell = aShell;
+
+  if (aBackendType == StyleBackendType::Servo) {
+    mRestyleManager = new ServoRestyleManager(this);
+  } else {
+    // Since RestyleManager is also the name of a method of nsPresContext,
+    // it is necessary to prefix the class with the mozilla namespace
+    // here.
+    mRestyleManager = new mozilla::RestyleManager(this);
+  }
+
+  // Since CounterStyleManager is also the name of a method of
+  // nsPresContext, it is necessary to prefix the class with the mozilla
+  // namespace here.
+  mCounterStyleManager = new mozilla::CounterStyleManager(this);
+
+  nsIDocument *doc = mShell->GetDocument();
+  NS_ASSERTION(doc, "expect document here");
+  if (doc) {
+    // Have to update PresContext's mDocument before calling any other methods.
+    mDocument = doc;
+  }
+  // Initialize our state from the user preferences, now that we
+  // have a presshell, and hence a document.
+  GetUserPreferences();
+
+  if (doc) {
+    nsIURI *docURI = doc->GetDocumentURI();
+
+    if (IsDynamic() && docURI) {
+      bool isChrome = false;
+      bool isRes = false;
+      docURI->SchemeIs("chrome", &isChrome);
+      docURI->SchemeIs("resource", &isRes);
+
+      if (!isChrome && !isRes)
+        mImageAnimationMode = mImageAnimationModePref;
+      else
+        mImageAnimationMode = imgIContainer::kNormalAnimMode;
+    }
+
+    if (mLangService) {
+      doc->AddCharSetObserver(this);
+      UpdateCharSet(doc->GetDocumentCharacterSet());
+    }
+  }
+}
+
+void
+nsPresContext::DetachShell()
+{
+  // Remove ourselves as the charset observer from the shell's doc, because
+  // this shell may be going away for good.
+  nsIDocument *doc = mShell ? mShell->GetDocument() : nullptr;
+  if (doc) {
+    doc->RemoveCharSetObserver(this);
+  }
+
+  // The counter style manager's destructor needs to deallocate with the
+  // presshell arena. Disconnect it before nulling out the shell.
+  //
+  // XXXbholley: Given recent refactorings, it probably makes more sense to
+  // just null our mShell at the bottom of this function. I'm leaving it
+  // this way to preserve the old ordering, but I doubt anything would break.
+  if (mCounterStyleManager) {
+    mCounterStyleManager->Disconnect();
+    mCounterStyleManager = nullptr;
+  }
+
+  mShell = nullptr;
+
+  if (mEffectCompositor) {
+    mEffectCompositor->Disconnect();
+    mEffectCompositor = nullptr;
+  }
+  if (mTransitionManager) {
+    mTransitionManager->Disconnect();
+    mTransitionManager = nullptr;
+  }
+  if (mAnimationManager) {
+    mAnimationManager->Disconnect();
+    mAnimationManager = nullptr;
+  }
+  if (mRestyleManager) {
+    mRestyleManager->Disconnect();
+    mRestyleManager = nullptr;
+  }
+  if (mRefreshDriver && mRefreshDriver->GetPresContext() == this) {
+    mRefreshDriver->Disconnect();
+    // Can't null out the refresh driver here.
+  }
+
+  if (IsRoot()) {
+    nsRootPresContext* thisRoot = static_cast<nsRootPresContext*>(this);
+
+    // Have to cancel our plugin geometry timer, because the
+    // callback for that depends on a non-null presshell.
+    thisRoot->CancelApplyPluginGeometryTimer();
+
+    // The did-paint timer also depends on a non-null pres shell.
+    thisRoot->CancelDidPaintTimer();
+  }
+}
+
+void
+nsPresContext::DoChangeCharSet(const nsCString& aCharSet)
+{
+  UpdateCharSet(aCharSet);
+  mDeviceContext->FlushFontCache();
+  RebuildAllStyleData(NS_STYLE_HINT_REFLOW, nsRestyleHint(0));
+}
+
+void
+nsPresContext::UpdateCharSet(const nsCString& aCharSet)
+{
+  if (mLangService) {
+    mLanguage = mLangService->LookupCharSet(aCharSet);
+    // this will be a language group (or script) code rather than a true language code
+
+    // bug 39570: moved from nsLanguageAtomService::LookupCharSet()
+    if (mLanguage == nsGkAtoms::Unicode) {
+      mLanguage = mLangService->GetLocaleLanguage();
+    }
+    mLangGroupFontPrefs.Reset();
+  }
+
+  switch (GET_BIDI_OPTION_TEXTTYPE(GetBidi())) {
+
+    case IBMBIDI_TEXTTYPE_LOGICAL:
+      SetVisualMode(false);
+      break;
+
+    case IBMBIDI_TEXTTYPE_VISUAL:
+      SetVisualMode(true);
+      break;
+
+    case IBMBIDI_TEXTTYPE_CHARSET:
+    default:
+      SetVisualMode(IsVisualCharset(aCharSet));
+  }
+}
+
+NS_IMETHODIMP
+nsPresContext::Observe(nsISupports* aSubject,
+                        const char* aTopic,
+                        const char16_t* aData)
+{
+  if (!nsCRT::strcmp(aTopic, "charset")) {
+    RefPtr<CharSetChangingRunnable> runnable =
+      new CharSetChangingRunnable(this, NS_LossyConvertUTF16toASCII(aData));
+    return NS_DispatchToCurrentThread(runnable);
+  }
+
+  NS_WARNING("unrecognized topic in nsPresContext::Observe");
+  return NS_ERROR_FAILURE;
+}
+
+nsPresContext*
+nsPresContext::GetParentPresContext()
+{
+  nsIPresShell* shell = GetPresShell();
+  if (shell) {
+    nsViewManager* viewManager = shell->GetViewManager();
+    if (viewManager) {
+      nsView* view = viewManager->GetRootView();
+      if (view) {
+        view = view->GetParent(); // anonymous inner view
+        if (view) {
+          view = view->GetParent(); // subdocumentframe's view
+          if (view) {
+            nsIFrame* f = view->GetFrame();
+            if (f) {
+              return f->PresContext();
+            }
+          }
+        }
+      }
+    }
+  }
+  return nullptr;
+}
+
+nsPresContext*
+nsPresContext::GetToplevelContentDocumentPresContext()
+{
+  if (IsChrome())
+    return nullptr;
+  nsPresContext* pc = this;
+  for (;;) {
+    nsPresContext* parent = pc->GetParentPresContext();
+    if (!parent || parent->IsChrome())
+      return pc;
+    pc = parent;
+  }
+}
+
+nsIWidget*
+nsPresContext::GetNearestWidget(nsPoint* aOffset)
+{
+  NS_ENSURE_TRUE(mShell, nullptr);
+  nsIFrame* frame = mShell->GetRootFrame();
+  NS_ENSURE_TRUE(frame, nullptr);
+  return frame->GetView()->GetNearestWidget(aOffset);
+}
+
+nsIWidget*
+nsPresContext::GetRootWidget()
+{
+  NS_ENSURE_TRUE(mShell, nullptr);
+  nsViewManager* vm = mShell->GetViewManager();
+  if (!vm) {
+    return nullptr;
+  }
+  nsCOMPtr<nsIWidget> widget;
+  vm->GetRootWidget(getter_AddRefs(widget));
+  return widget.get();
+}
+
+// We may want to replace this with something faster, maybe caching the root prescontext
+nsRootPresContext*
+nsPresContext::GetRootPresContext()
+{
+  nsPresContext* pc = this;
+  for (;;) {
+    nsPresContext* parent = pc->GetParentPresContext();
+    if (!parent)
+      break;
+    pc = parent;
+  }
+  return pc->IsRoot() ? static_cast<nsRootPresContext*>(pc) : nullptr;
+}
+
+void
+nsPresContext::CompatibilityModeChanged()
+{
+  if (!mShell) {
+    return;
+  }
+
+  nsIDocument* doc = mShell->GetDocument();
+  if (!doc) {
+    return;
+  }
+
+  if (doc->IsSVGDocument()) {
+    // SVG documents never load quirk.css.
+    return;
+  }
+
+  bool needsQuirkSheet = CompatibilityMode() == eCompatibility_NavQuirks;
+  if (mQuirkSheetAdded == needsQuirkSheet) {
+    return;
+  }
+
+  StyleSetHandle styleSet = mShell->StyleSet();
+  auto cache = nsLayoutStylesheetCache::For(styleSet->BackendType());
+  StyleSheet* sheet = cache->QuirkSheet();
+
+  if (needsQuirkSheet) {
+    // quirk.css needs to come after html.css; we just keep it at the end.
+    DebugOnly<nsresult> rv =
+      styleSet->AppendStyleSheet(SheetType::Agent, sheet);
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "failed to insert quirk.css");
+  } else {
+    DebugOnly<nsresult> rv =
+      styleSet->RemoveStyleSheet(SheetType::Agent, sheet);
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "failed to remove quirk.css");
+  }
+
+  mQuirkSheetAdded = needsQuirkSheet;
+}
+
+// Helper function for setting Anim Mode on image
+static void SetImgAnimModeOnImgReq(imgIRequest* aImgReq, uint16_t aMode)
+{
+  if (aImgReq) {
+    nsCOMPtr<imgIContainer> imgCon;
+    aImgReq->GetImage(getter_AddRefs(imgCon));
+    if (imgCon) {
+      imgCon->SetAnimationMode(aMode);
+    }
+  }
+}
+
+// IMPORTANT: Assumption is that all images for a Presentation
+// have the same Animation Mode (pavlov said this was OK)
+//
+// Walks content and set the animation mode
+// this is a way to turn on/off image animations
+void nsPresContext::SetImgAnimations(nsIContent *aParent, uint16_t aMode)
+{
+  nsCOMPtr<nsIImageLoadingContent> imgContent(do_QueryInterface(aParent));
+  if (imgContent) {
+    nsCOMPtr<imgIRequest> imgReq;
+    imgContent->GetRequest(nsIImageLoadingContent::CURRENT_REQUEST,
+                           getter_AddRefs(imgReq));
+    SetImgAnimModeOnImgReq(imgReq, aMode);
+  }
+
+  uint32_t count = aParent->GetChildCount();
+  for (uint32_t i = 0; i < count; ++i) {
+    SetImgAnimations(aParent->GetChildAt(i), aMode);
+  }
+}
+
+void
+nsPresContext::SetSMILAnimations(nsIDocument *aDoc, uint16_t aNewMode,
+                                 uint16_t aOldMode)
+{
+  if (aDoc->HasAnimationController()) {
+    nsSMILAnimationController* controller = aDoc->GetAnimationController();
+    switch (aNewMode)
+    {
+      case imgIContainer::kNormalAnimMode:
+      case imgIContainer::kLoopOnceAnimMode:
+        if (aOldMode == imgIContainer::kDontAnimMode)
+          controller->Resume(nsSMILTimeContainer::PAUSE_USERPREF);
+        break;
+
+      case imgIContainer::kDontAnimMode:
+        if (aOldMode != imgIContainer::kDontAnimMode)
+          controller->Pause(nsSMILTimeContainer::PAUSE_USERPREF);
+        break;
+    }
+  }
+}
+
+void
+nsPresContext::SetImageAnimationModeInternal(uint16_t aMode)
+{
+  NS_ASSERTION(aMode == imgIContainer::kNormalAnimMode ||
+               aMode == imgIContainer::kDontAnimMode ||
+               aMode == imgIContainer::kLoopOnceAnimMode, "Wrong Animation Mode is being set!");
+
+  // Image animation mode cannot be changed when rendering to a printer.
+  if (!IsDynamic())
+    return;
+
+  // Now walk the content tree and set the animation mode
+  // on all the images.
+  if (mShell != nullptr) {
+    nsIDocument *doc = mShell->GetDocument();
+    if (doc) {
+      doc->StyleImageLoader()->SetAnimationMode(aMode);
+
+      Element *rootElement = doc->GetRootElement();
+      if (rootElement) {
+        SetImgAnimations(rootElement, aMode);
+      }
+      SetSMILAnimations(doc, aMode, mImageAnimationMode);
+    }
+  }
+
+  mImageAnimationMode = aMode;
+}
+
+void
+nsPresContext::SetImageAnimationModeExternal(uint16_t aMode)
+{
+  SetImageAnimationModeInternal(aMode);
+}
+
+already_AddRefed<nsIAtom>
+nsPresContext::GetContentLanguage() const
+{
+  nsAutoString language;
+  Document()->GetContentLanguage(language);
+  language.StripWhitespace();
+
+  // Content-Language may be a comma-separated list of language codes,
+  // in which case the HTML5 spec says to treat it as unknown
+  if (!language.IsEmpty() &&
+      !language.Contains(char16_t(','))) {
+    return NS_Atomize(language);
+    // NOTE:  This does *not* count as an explicit language; in other
+    // words, it doesn't trigger language-specific hyphenation.
+  }
+  return nullptr;
+}
+
+void
+nsPresContext::SetFullZoom(float aZoom)
+{
+  if (!mShell || mFullZoom == aZoom) {
+    return;
+  }
+
+  // Re-fetch the view manager's window dimensions in case there's a deferred
+  // resize which hasn't affected our mVisibleArea yet
+  nscoord oldWidthAppUnits, oldHeightAppUnits;
+  mShell->GetViewManager()->GetWindowDimensions(&oldWidthAppUnits, &oldHeightAppUnits);
+  float oldWidthDevPixels = oldWidthAppUnits / float(mCurAppUnitsPerDevPixel);
+  float oldHeightDevPixels = oldHeightAppUnits / float(mCurAppUnitsPerDevPixel);
+  mDeviceContext->SetFullZoom(aZoom);
+
+  NS_ASSERTION(!mSuppressResizeReflow, "two zooms happening at the same time? impossible!");
+  mSuppressResizeReflow = true;
+
+  mFullZoom = aZoom;
+  mShell->GetViewManager()->
+    SetWindowDimensions(NSToCoordRound(oldWidthDevPixels * AppUnitsPerDevPixel()),
+                        NSToCoordRound(oldHeightDevPixels * AppUnitsPerDevPixel()));
+
+  AppUnitsPerDevPixelChanged();
+
+  mSuppressResizeReflow = false;
+}
+
+void
+nsPresContext::SetOverrideDPPX(float aDPPX)
+{
+  mOverrideDPPX = aDPPX;
+
+  if (HasCachedStyleData()) {
+    MediaFeatureValuesChanged(nsRestyleHint(0), nsChangeHint(0));
+  }
+}
+
+gfxSize
+nsPresContext::ScreenSizeInchesForFontInflation(bool* aChanged)
+{
+  if (aChanged) {
+    *aChanged = false;
+  }
+
+  nsDeviceContext *dx = DeviceContext();
+  nsRect clientRect;
+  dx->GetClientRect(clientRect); // FIXME: GetClientRect looks expensive
+  float unitsPerInch = dx->AppUnitsPerPhysicalInch();
+  gfxSize deviceSizeInches(float(clientRect.width) / unitsPerInch,
+                           float(clientRect.height) / unitsPerInch);
+
+  if (mLastFontInflationScreenSize == gfxSize(-1.0, -1.0)) {
+    mLastFontInflationScreenSize = deviceSizeInches;
+  }
+
+  if (deviceSizeInches != mLastFontInflationScreenSize && aChanged) {
+    *aChanged = true;
+    mLastFontInflationScreenSize = deviceSizeInches;
+  }
+
+  return deviceSizeInches;
+}
+
+static bool
+CheckOverflow(const nsStyleDisplay* aDisplay, ScrollbarStyles* aStyles)
+{
+  if (aDisplay->mOverflowX == NS_STYLE_OVERFLOW_VISIBLE &&
+      aDisplay->mScrollBehavior == NS_STYLE_SCROLL_BEHAVIOR_AUTO &&
+      aDisplay->mScrollSnapTypeX == NS_STYLE_SCROLL_SNAP_TYPE_NONE &&
+      aDisplay->mScrollSnapTypeY == NS_STYLE_SCROLL_SNAP_TYPE_NONE &&
+      aDisplay->mScrollSnapPointsX == nsStyleCoord(eStyleUnit_None) &&
+      aDisplay->mScrollSnapPointsY == nsStyleCoord(eStyleUnit_None) &&
+      !aDisplay->mScrollSnapDestination.mXPosition.mHasPercent &&
+      !aDisplay->mScrollSnapDestination.mYPosition.mHasPercent &&
+      aDisplay->mScrollSnapDestination.mXPosition.mLength == 0 &&
+      aDisplay->mScrollSnapDestination.mYPosition.mLength == 0) {
+    return false;
+  }
+
+  if (aDisplay->mOverflowX == NS_STYLE_OVERFLOW_CLIP) {
+    *aStyles = ScrollbarStyles(NS_STYLE_OVERFLOW_HIDDEN,
+                               NS_STYLE_OVERFLOW_HIDDEN, aDisplay);
+  } else {
+    *aStyles = ScrollbarStyles(aDisplay);
+  }
+  return true;
+}
+
+static nsIContent*
+GetPropagatedScrollbarStylesForViewport(nsPresContext* aPresContext,
+                                        ScrollbarStyles *aStyles)
+{
+  nsIDocument* document = aPresContext->Document();
+  Element* docElement = document->GetRootElement();
+
+  // docElement might be null if we're doing this after removing it.
+  if (!docElement) {
+    return nullptr;
+  }
+
+  // Check the style on the document root element
+  StyleSetHandle styleSet = aPresContext->StyleSet();
+  RefPtr<nsStyleContext> rootStyle;
+  rootStyle = styleSet->ResolveStyleFor(docElement, nullptr);
+  if (CheckOverflow(rootStyle->StyleDisplay(), aStyles)) {
+    // tell caller we stole the overflow style from the root element
+    return docElement;
+  }
+
+  // Don't look in the BODY for non-HTML documents or HTML documents
+  // with non-HTML roots
+  // XXX this should be earlier; we shouldn't even look at the document root
+  // for non-HTML documents. Fix this once we support explicit CSS styling
+  // of the viewport
+  // XXX what about XHTML?
+  nsCOMPtr<nsIDOMHTMLDocument> htmlDoc(do_QueryInterface(document));
+  if (!htmlDoc || !docElement->IsHTMLElement()) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIDOMHTMLElement> body;
+  htmlDoc->GetBody(getter_AddRefs(body));
+  nsCOMPtr<nsIContent> bodyElement = do_QueryInterface(body);
+
+  if (!bodyElement ||
+      !bodyElement->NodeInfo()->Equals(nsGkAtoms::body)) {
+    // The body is not a <body> tag, it's a <frameset>.
+    return nullptr;
+  }
+
+  RefPtr<nsStyleContext> bodyStyle;
+  bodyStyle = styleSet->ResolveStyleFor(bodyElement->AsElement(), rootStyle);
+
+  if (CheckOverflow(bodyStyle->StyleDisplay(), aStyles)) {
+    // tell caller we stole the overflow style from the body element
+    return bodyElement;
+  }
+
+  return nullptr;
+}
+
+nsIContent*
+nsPresContext::UpdateViewportScrollbarStylesOverride()
+{
+  // Start off with our default styles, and then update them as needed.
+  mViewportStyleScrollbar = ScrollbarStyles(NS_STYLE_OVERFLOW_AUTO,
+                                            NS_STYLE_OVERFLOW_AUTO);
+  nsIContent* propagatedFrom = nullptr;
+  // Don't propagate the scrollbar state in printing or print preview.
+  if (!IsPaginated()) {
+    propagatedFrom =
+      GetPropagatedScrollbarStylesForViewport(this, &mViewportStyleScrollbar);
+  }
+
+  nsIDocument* document = Document();
+  if (Element* fullscreenElement = document->GetFullscreenElement()) {
+    // If the document is in fullscreen, but the fullscreen element is
+    // not the root element, we should explicitly suppress the scrollbar
+    // here. Note that, we still need to return the original element
+    // the styles are from, so that the state of those elements is not
+    // affected across fullscreen change.
+    if (fullscreenElement != document->GetRootElement() &&
+        fullscreenElement != propagatedFrom) {
+      mViewportStyleScrollbar = ScrollbarStyles(NS_STYLE_OVERFLOW_HIDDEN,
+                                                NS_STYLE_OVERFLOW_HIDDEN);
+    }
+  }
+
+  return propagatedFrom;
+}
+
+bool
+nsPresContext::ElementWouldPropagateScrollbarStyles(Element* aElement)
+{
+  MOZ_ASSERT(IsPaginated(), "Should only be called on paginated contexts");
+  if (aElement->GetParent() && !aElement->IsHTMLElement(nsGkAtoms::body)) {
+    // We certainly won't be propagating from this element.
+    return false;
+  }
+
+  // Go ahead and just call GetPropagatedScrollbarStylesForViewport, but update
+  // a dummy ScrollbarStyles we don't care about.  It'll do a bit of extra work,
+  // but saves us having to have more complicated code or more code duplication;
+  // in practice we will make this call quite rarely, because we checked for all
+  // the common cases above.
+  ScrollbarStyles dummy(NS_STYLE_OVERFLOW_AUTO, NS_STYLE_OVERFLOW_AUTO);
+  return GetPropagatedScrollbarStylesForViewport(this, &dummy) == aElement;
+}
+
+void
+nsPresContext::SetContainer(nsIDocShell* aDocShell)
+{
+  if (aDocShell) {
+    NS_ASSERTION(!(mContainer && mNeedsPrefUpdate),
+                 "Should only need pref update if mContainer is null.");
+    mContainer = static_cast<nsDocShell*>(aDocShell);
+    if (mNeedsPrefUpdate) {
+      if (!mPrefChangedTimer) {
+        mPrefChangedTimer = CreateTimer(PrefChangedUpdateTimerCallback, 0);
+      }
+      mNeedsPrefUpdate = false;
+    }
+  } else {
+    mContainer = WeakPtr<nsDocShell>();
+  }
+  UpdateIsChrome();
+  if (mContainer) {
+    GetDocumentColorPreferences();
+  }
+}
+
+nsISupports*
+nsPresContext::GetContainerWeakInternal() const
+{
+  return static_cast<nsIDocShell*>(mContainer);
+}
+
+nsISupports*
+nsPresContext::GetContainerWeakExternal() const
+{
+  return GetContainerWeakInternal();
+}
+
+nsIDocShell*
+nsPresContext::GetDocShell() const
+{
+  return mContainer;
+}
+
+/* virtual */ void
+nsPresContext::Detach()
+{
+  SetContainer(nullptr);
+  SetLinkHandler(nullptr);
+  if (mShell) {
+    mShell->CancelInvalidatePresShellIfHidden();
+  }
+}
+
+bool
+nsPresContext::BidiEnabledExternal() const
+{
+  return BidiEnabledInternal();
+}
+
+bool
+nsPresContext::BidiEnabledInternal() const
+{
+  return Document()->GetBidiEnabled();
+}
+
+void
+nsPresContext::SetBidiEnabled() const
+{
+  if (mShell) {
+    nsIDocument *doc = mShell->GetDocument();
+    if (doc) {
+      doc->SetBidiEnabled();
+    }
+  }
+}
+
+void
+nsPresContext::SetBidi(uint32_t aSource, bool aForceRestyle)
+{
+  // Don't do all this stuff unless the options have changed.
+  if (aSource == GetBidi()) {
+    return;
+  }
+
+  NS_ASSERTION(!(aForceRestyle && (GetBidi() == 0)),
+               "ForceReflow on new prescontext");
+
+  Document()->SetBidiOptions(aSource);
+  if (IBMBIDI_TEXTDIRECTION_RTL == GET_BIDI_OPTION_DIRECTION(aSource)
+      || IBMBIDI_NUMERAL_HINDI == GET_BIDI_OPTION_NUMERAL(aSource)) {
+    SetBidiEnabled();
+  }
+  if (IBMBIDI_TEXTTYPE_VISUAL == GET_BIDI_OPTION_TEXTTYPE(aSource)) {
+    SetVisualMode(true);
+  }
+  else if (IBMBIDI_TEXTTYPE_LOGICAL == GET_BIDI_OPTION_TEXTTYPE(aSource)) {
+    SetVisualMode(false);
+  }
+  else {
+    nsIDocument* doc = mShell->GetDocument();
+    if (doc) {
+      SetVisualMode(IsVisualCharset(doc->GetDocumentCharacterSet()));
+    }
+  }
+  if (aForceRestyle && mShell) {
+    // Reconstruct the root document element's frame and its children,
+    // because we need to trigger frame reconstruction for direction change.
+    mDocument->RebuildUserFontSet();
+    mShell->ReconstructFrames();
+  }
+}
+
+uint32_t
+nsPresContext::GetBidi() const
+{
+  return Document()->GetBidiOptions();
+}
+
+bool
+nsPresContext::IsTopLevelWindowInactive()
+{
+  nsCOMPtr<nsIDocShellTreeItem> treeItem(mContainer);
+  if (!treeItem)
+    return false;
+
+  nsCOMPtr<nsIDocShellTreeItem> rootItem;
+  treeItem->GetRootTreeItem(getter_AddRefs(rootItem));
+  if (!rootItem) {
+    return false;
+  }
+
+  nsCOMPtr<nsPIDOMWindowOuter> domWindow = rootItem->GetWindow();
+
+  return domWindow && !domWindow->IsActive();
+}
+
+nsITheme*
+nsPresContext::GetTheme()
+{
+  if (!sNoTheme && !mTheme) {
+    mTheme = do_GetService("@mozilla.org/chrome/chrome-native-theme;1");
+    if (!mTheme)
+      sNoTheme = true;
+  }
+
+  return mTheme;
+}
+
+void
+nsPresContext::ThemeChanged()
+{
+  if (!mPendingThemeChanged) {
+    sLookAndFeelChanged = true;
+    sThemeChanged = true;
+
+    nsCOMPtr<nsIRunnable> ev =
+      NewRunnableMethod(this, &nsPresContext::ThemeChangedInternal);
+    if (NS_SUCCEEDED(NS_DispatchToCurrentThread(ev))) {
+      mPendingThemeChanged = true;
+    }
+  }
+}
+
+static bool
+NotifyThemeChanged(TabParent* aTabParent, void* aArg)
+{
+  aTabParent->ThemeChanged();
+  return false;
+}
+
+void
+nsPresContext::ThemeChangedInternal()
+{
+  mPendingThemeChanged = false;
+
+  // Tell the theme that it changed, so it can flush any handles to stale theme
+  // data.
+  if (mTheme && sThemeChanged) {
+    mTheme->ThemeChanged();
+    sThemeChanged = false;
+  }
+
+  if (sLookAndFeelChanged) {
+    // Clear all cached LookAndFeel colors.
+    LookAndFeel::Refresh();
+    sLookAndFeelChanged = false;
+
+    // Vector images (SVG) may be using theme colors so we discard all cached
+    // surfaces. (We could add a vector image only version of DiscardAll, but
+    // in bug 940625 we decided theme changes are rare enough not to bother.)
+    image::SurfaceCacheUtils::DiscardAll();
+  }
+
+  // This will force the system metrics to be generated the next time they're used
+  nsCSSRuleProcessor::FreeSystemMetrics();
+
+  // Changes to system metrics can change media queries on them, or
+  // :-moz-system-metric selectors (which requires eRestyle_Subtree).
+  // Changes in theme can change system colors (whose changes are
+  // properly reflected in computed style data), system fonts (whose
+  // changes are not), and -moz-appearance (whose changes likewise are
+  // not), so we need to reflow.
+  MediaFeatureValuesChanged(eRestyle_Subtree, NS_STYLE_HINT_REFLOW);
+
+  // Recursively notify all remote leaf descendants that the
+  // system theme has changed.
+  nsContentUtils::CallOnAllRemoteChildren(mDocument->GetWindow(),
+                                          NotifyThemeChanged, nullptr);
+}
+
+void
+nsPresContext::SysColorChanged()
+{
+  if (!mPendingSysColorChanged) {
+    sLookAndFeelChanged = true;
+    nsCOMPtr<nsIRunnable> ev =
+      NewRunnableMethod(this, &nsPresContext::SysColorChangedInternal);
+    if (NS_SUCCEEDED(NS_DispatchToCurrentThread(ev))) {
+      mPendingSysColorChanged = true;
+    }
+  }
+}
+
+void
+nsPresContext::SysColorChangedInternal()
+{
+  mPendingSysColorChanged = false;
+
+  if (sLookAndFeelChanged) {
+     // Don't use the cached values for the system colors
+    LookAndFeel::Refresh();
+    sLookAndFeelChanged = false;
+  }
+
+  // Reset default background and foreground colors for the document since
+  // they may be using system colors
+  GetDocumentColorPreferences();
+
+  // The system color values are computed to colors in the style data,
+  // so normal style data comparison is sufficient here.
+  RebuildAllStyleData(nsChangeHint(0), nsRestyleHint(0));
+}
+
+void
+nsPresContext::UIResolutionChanged()
+{
+  if (!mPendingUIResolutionChanged) {
+    nsCOMPtr<nsIRunnable> ev =
+      NewRunnableMethod(this, &nsPresContext::UIResolutionChangedInternal);
+    if (NS_SUCCEEDED(NS_DispatchToCurrentThread(ev))) {
+      mPendingUIResolutionChanged = true;
+    }
+  }
+}
+
+void
+nsPresContext::UIResolutionChangedSync()
+{
+  if (!mPendingUIResolutionChanged) {
+    mPendingUIResolutionChanged = true;
+    UIResolutionChangedInternalScale(0.0);
+  }
+}
+
+/*static*/ bool
+nsPresContext::UIResolutionChangedSubdocumentCallback(nsIDocument* aDocument,
+                                                      void* aData)
+{
+  nsIPresShell* shell = aDocument->GetShell();
+  if (shell) {
+    nsPresContext* pc = shell->GetPresContext();
+    if (pc) {
+      // For subdocuments, we want to apply the parent's scale, because there
+      // are cases where the subdoc's device context is connected to a widget
+      // that has an out-of-date resolution (it's on a different screen, but
+      // currently hidden, and will not be updated until shown): bug 1249279.
+      double scale = *static_cast<double*>(aData);
+      pc->UIResolutionChangedInternalScale(scale);
+    }
+  }
+  return true;
+}
+
+static void
+NotifyTabUIResolutionChanged(TabParent* aTab, void *aArg)
+{
+  aTab->UIResolutionChanged();
+}
+
+static void
+NotifyChildrenUIResolutionChanged(nsPIDOMWindowOuter* aWindow)
+{
+  nsCOMPtr<nsIDocument> doc = aWindow->GetExtantDoc();
+  RefPtr<nsPIWindowRoot> topLevelWin = nsContentUtils::GetWindowRoot(doc);
+  if (!topLevelWin) {
+    return;
+  }
+  topLevelWin->EnumerateBrowsers(NotifyTabUIResolutionChanged, nullptr);
+}
+
+void
+nsPresContext::UIResolutionChangedInternal()
+{
+  UIResolutionChangedInternalScale(0.0);
+}
+
+void
+nsPresContext::UIResolutionChangedInternalScale(double aScale)
+{
+  mPendingUIResolutionChanged = false;
+
+  mDeviceContext->CheckDPIChange(&aScale);
+  if (mCurAppUnitsPerDevPixel != AppUnitsPerDevPixel()) {
+    AppUnitsPerDevPixelChanged();
+  }
+
+  // Recursively notify all remote leaf descendants of the change.
+  if (nsPIDOMWindowOuter* window = mDocument->GetWindow()) {
+    NotifyChildrenUIResolutionChanged(window);
+  }
+
+  mDocument->EnumerateSubDocuments(UIResolutionChangedSubdocumentCallback,
+                                   &aScale);
+}
+
+void
+nsPresContext::EmulateMedium(const nsAString& aMediaType)
+{
+  nsIAtom* previousMedium = Medium();
+  mIsEmulatingMedia = true;
+
+  nsAutoString mediaType;
+  nsContentUtils::ASCIIToLower(aMediaType, mediaType);
+
+  mMediaEmulated = NS_Atomize(mediaType);
+  if (mMediaEmulated != previousMedium && mShell) {
+    MediaFeatureValuesChanged(nsRestyleHint(0), nsChangeHint(0));
+  }
+}
+
+void nsPresContext::StopEmulatingMedium()
+{
+  nsIAtom* previousMedium = Medium();
+  mIsEmulatingMedia = false;
+  if (Medium() != previousMedium) {
+    MediaFeatureValuesChanged(nsRestyleHint(0), nsChangeHint(0));
+  }
+}
+
+void
+nsPresContext::RebuildAllStyleData(nsChangeHint aExtraHint,
+                                   nsRestyleHint aRestyleHint)
+{
+  if (!mShell) {
+    // We must have been torn down. Nothing to do here.
+    return;
+  }
+
+  mUsesRootEMUnits = false;
+  mUsesExChUnits = false;
+  mUsesViewportUnits = false;
+  mDocument->RebuildUserFontSet();
+  RebuildCounterStyles();
+
+  RestyleManager()->RebuildAllStyleData(aExtraHint, aRestyleHint);
+}
+
+void
+nsPresContext::PostRebuildAllStyleDataEvent(nsChangeHint aExtraHint,
+                                            nsRestyleHint aRestyleHint)
+{
+  if (!mShell) {
+    // We must have been torn down. Nothing to do here.
+    return;
+  }
+  RestyleManager()->PostRebuildAllStyleDataEvent(aExtraHint, aRestyleHint);
+}
+
+struct MediaFeatureHints
+{
+  nsRestyleHint restyleHint;
+  nsChangeHint changeHint;
+};
+
+static bool
+MediaFeatureValuesChangedAllDocumentsCallback(nsIDocument* aDocument, void* aHints)
+{
+  MediaFeatureHints* hints = static_cast<MediaFeatureHints*>(aHints);
+  if (nsIPresShell* shell = aDocument->GetShell()) {
+    if (nsPresContext* pc = shell->GetPresContext()) {
+      pc->MediaFeatureValuesChangedAllDocuments(hints->restyleHint,
+                                                hints->changeHint);
+    }
+  }
+  return true;
+}
+
+void
+nsPresContext::MediaFeatureValuesChangedAllDocuments(nsRestyleHint aRestyleHint,
+                                                     nsChangeHint aChangeHint)
+{
+    MediaFeatureValuesChanged(aRestyleHint, aChangeHint);
+    MediaFeatureHints hints = {
+      aRestyleHint,
+      aChangeHint
+    };
+
+    mDocument->EnumerateSubDocuments(MediaFeatureValuesChangedAllDocumentsCallback,
+                                     &hints);
+}
+
+void
+nsPresContext::MediaFeatureValuesChanged(nsRestyleHint aRestyleHint,
+                                         nsChangeHint aChangeHint)
+{
+  mPendingMediaFeatureValuesChanged = false;
+
+  // MediumFeaturesChanged updates the applied rules, so it always gets called.
+  if (mShell) {
+    // XXXheycam ServoStyleSets don't support responding to medium
+    // changes yet.
+    if (mShell->StyleSet()->IsGecko()) {
+      if (mShell->StyleSet()->AsGecko()->MediumFeaturesChanged()) {
+        aRestyleHint |= eRestyle_Subtree;
+      }
+    } else {
+      NS_WARNING("stylo: ServoStyleSets don't support responding to medium "
+                 "changes yet. See bug 1290228.");
+    }
+  }
+
+  if (mUsesViewportUnits && mPendingViewportChange) {
+    // Rebuild all style data without rerunning selector matching.
+    aRestyleHint |= eRestyle_ForceDescendants;
+  }
+
+  if (aRestyleHint || aChangeHint) {
+    RebuildAllStyleData(aChangeHint, aRestyleHint);
+  }
+
+  mPendingViewportChange = false;
+
+  if (mDocument->IsBeingUsedAsImage()) {
+    MOZ_ASSERT(PR_CLIST_IS_EMPTY(mDocument->MediaQueryLists()));
+    return;
+  }
+
+  mDocument->NotifyMediaFeatureValuesChanged();
+
+  MOZ_ASSERT(nsContentUtils::IsSafeToRunScript());
+
+  // Media query list listeners should be notified from a queued task
+  // (in HTML5 terms), although we also want to notify them on certain
+  // flushes.  (We're already running off an event.)
+  //
+  // Note that we do this after the new style from media queries in
+  // style sheets has been computed.
+
+  if (!PR_CLIST_IS_EMPTY(mDocument->MediaQueryLists())) {
+    // We build a list of all the notifications we're going to send
+    // before we send any of them.  (The spec says the notifications
+    // should be a queued task, so any removals that happen during the
+    // notifications shouldn't affect what gets notified.)  Furthermore,
+    // we hold strong pointers to everything we're going to make
+    // notification calls to, since each notification involves calling
+    // arbitrary script that might otherwise destroy these objects, or,
+    // for that matter, |this|.
+    //
+    // Note that we intentionally send the notifications to media query
+    // list in the order they were created and, for each list, to the
+    // listeners in the order added.
+    nsTArray<MediaQueryList::HandleChangeData> notifyList;
+    for (PRCList *l = PR_LIST_HEAD(mDocument->MediaQueryLists());
+         l != mDocument->MediaQueryLists(); l = PR_NEXT_LINK(l)) {
+      MediaQueryList *mql = static_cast<MediaQueryList*>(l);
+      mql->MediumFeaturesChanged(notifyList);
+    }
+
+    if (!notifyList.IsEmpty()) {
+      for (uint32_t i = 0, i_end = notifyList.Length(); i != i_end; ++i) {
+        nsAutoMicroTask mt;
+        MediaQueryList::HandleChangeData &d = notifyList[i];
+        d.callback->Call(*d.mql);
+      }
+    }
+
+    // NOTE:  When |notifyList| goes out of scope, our destructor could run.
+  }
+}
+
+void
+nsPresContext::PostMediaFeatureValuesChangedEvent()
+{
+  // FIXME: We should probably replace this event with use of
+  // nsRefreshDriver::AddStyleFlushObserver (except the pres shell would
+  // need to track whether it's been added).
+  if (!mPendingMediaFeatureValuesChanged) {
+    nsCOMPtr<nsIRunnable> ev =
+      NewRunnableMethod(this, &nsPresContext::HandleMediaFeatureValuesChangedEvent);
+    if (NS_SUCCEEDED(NS_DispatchToCurrentThread(ev))) {
+      mPendingMediaFeatureValuesChanged = true;
+      mDocument->SetNeedStyleFlush();
+    }
+  }
+}
+
+void
+nsPresContext::HandleMediaFeatureValuesChangedEvent()
+{
+  // Null-check mShell in case the shell has been destroyed (and the
+  // event is the only thing holding the pres context alive).
+  if (mPendingMediaFeatureValuesChanged && mShell) {
+    MediaFeatureValuesChanged(nsRestyleHint(0));
+  }
+}
+
+static bool
+NotifyTabSizeModeChanged(TabParent* aTab, void* aArg)
+{
+  nsSizeMode* sizeMode = static_cast<nsSizeMode*>(aArg);
+  aTab->SizeModeChanged(*sizeMode);
+  return false;
+}
+
+void
+nsPresContext::SizeModeChanged(nsSizeMode aSizeMode)
+{
+  if (HasCachedStyleData()) {
+    nsContentUtils::CallOnAllRemoteChildren(mDocument->GetWindow(),
+                                            NotifyTabSizeModeChanged,
+                                            &aSizeMode);
+    MediaFeatureValuesChangedAllDocuments(nsRestyleHint(0));
+  }
+}
+
+nsCompatibility
+nsPresContext::CompatibilityMode() const
+{
+  return Document()->GetCompatibilityMode();
+}
+
+void
+nsPresContext::SetPaginatedScrolling(bool aPaginated)
+{
+  if (mType == eContext_PrintPreview || mType == eContext_PageLayout)
+    mCanPaginatedScroll = aPaginated;
+}
+
+void
+nsPresContext::SetPrintSettings(nsIPrintSettings *aPrintSettings)
+{
+  if (mMedium == nsGkAtoms::print)
+    mPrintSettings = aPrintSettings;
+}
+
+bool
+nsPresContext::EnsureVisible()
+{
+  nsCOMPtr<nsIDocShell> docShell(mContainer);
+  if (docShell) {
+    nsCOMPtr<nsIContentViewer> cv;
+    docShell->GetContentViewer(getter_AddRefs(cv));
+    // Make sure this is the content viewer we belong with
+    if (cv) {
+      RefPtr<nsPresContext> currentPresContext;
+      cv->GetPresContext(getter_AddRefs(currentPresContext));
+      if (currentPresContext == this) {
+        // OK, this is us.  We want to call Show() on the content viewer.
+        nsresult result = cv->Show();
+        if (NS_SUCCEEDED(result)) {
+          return true;
+        }
+      }
+    }
+  }
+  return false;
+}
+
+#ifdef MOZ_REFLOW_PERF
+void
+nsPresContext::CountReflows(const char * aName, nsIFrame * aFrame)
+{
+  if (mShell) {
+    mShell->CountReflows(aName, aFrame);
+  }
+}
+#endif
+
+void
+nsPresContext::UpdateIsChrome()
+{
+  mIsChrome = mContainer &&
+              nsIDocShellTreeItem::typeChrome == mContainer->ItemType();
+}
+
+bool
+nsPresContext::HasAuthorSpecifiedRules(const nsIFrame *aFrame,
+                                       uint32_t ruleTypeMask) const
+{
+  return
+    nsRuleNode::HasAuthorSpecifiedRules(aFrame->StyleContext(),
+                                        ruleTypeMask,
+                                        UseDocumentColors());
+}
+
+gfxUserFontSet*
+nsPresContext::GetUserFontSet(bool aFlushUserFontSet)
+{
+  return mDocument->GetUserFontSet(aFlushUserFontSet);
+}
+
+void
+nsPresContext::UserFontSetUpdated(gfxUserFontEntry* aUpdatedFont)
+{
+  if (!mShell)
+    return;
+
+  bool usePlatformFontList = true;
+#if defined(MOZ_WIDGET_GTK)
+  usePlatformFontList = gfxPlatformGtk::UseFcFontList();
+#endif
+
+  // xxx - until the Linux platform font list is always used, use full
+  // restyle to force updates with gfxPangoFontGroup usage
+  // Note: this method is called without a font when rules in the userfont set
+  // are updated, which may occur during reflow as a result of the lazy
+  // initialization of the userfont set. It would be better to avoid a full
+  // restyle but until this method is only called outside of reflow, schedule a
+  // full restyle in these cases.
+  if (!usePlatformFontList || !aUpdatedFont) {
+    PostRebuildAllStyleDataEvent(NS_STYLE_HINT_REFLOW, eRestyle_ForceDescendants);
+    return;
+  }
+
+  // Special case - if either the 'ex' or 'ch' units are used, these
+  // depend upon font metrics. Updating this information requires
+  // rebuilding the rule tree from the top, avoiding the reuse of cached
+  // data even when no style rules have changed.
+  if (UsesExChUnits()) {
+    PostRebuildAllStyleDataEvent(nsChangeHint(0), eRestyle_ForceDescendants);
+  }
+
+  // Iterate over the frame tree looking for frames associated with the
+  // downloadable font family in question. If a frame's nsStyleFont has
+  // the name, check the font group associated with the metrics to see if
+  // it contains that specific font (i.e. the one chosen within the family
+  // given the weight, width, and slant from the nsStyleFont). If it does,
+  // mark that frame dirty and skip inspecting its descendants.
+  nsIFrame* root = mShell->GetRootFrame();
+  if (root) {
+    nsFontFaceUtils::MarkDirtyForFontChange(root, aUpdatedFont);
+  }
+}
+
+void
+nsPresContext::FlushCounterStyles()
+{
+  if (!mShell) {
+    return; // we've been torn down
+  }
+  if (mCounterStyleManager->IsInitial()) {
+    // Still in its initial state, no need to clean.
+    return;
+  }
+
+  if (mCounterStylesDirty) {
+    bool changed = mCounterStyleManager->NotifyRuleChanged();
+    if (changed) {
+      PresShell()->NotifyCounterStylesAreDirty();
+      PostRebuildAllStyleDataEvent(NS_STYLE_HINT_REFLOW,
+                                   eRestyle_ForceDescendants);
+    }
+    mCounterStylesDirty = false;
+  }
+}
+
+void
+nsPresContext::RebuildCounterStyles()
+{
+  if (mCounterStyleManager->IsInitial()) {
+    // Still in its initial state, no need to reset.
+    return;
+  }
+
+  mCounterStylesDirty = true;
+  mDocument->SetNeedStyleFlush();
+  if (!mPostedFlushCounterStyles) {
+    nsCOMPtr<nsIRunnable> ev =
+      NewRunnableMethod(this, &nsPresContext::HandleRebuildCounterStyles);
+    if (NS_SUCCEEDED(NS_DispatchToCurrentThread(ev))) {
+      mPostedFlushCounterStyles = true;
+    }
+  }
+}
+
+void
+nsPresContext::NotifyMissingFonts()
+{
+  if (mMissingFonts) {
+    mMissingFonts->Flush();
+  }
+}
+
+void
+nsPresContext::EnsureSafeToHandOutCSSRules()
+{
+  nsStyleSet* styleSet = mShell->StyleSet()->GetAsGecko();
+  if (!styleSet) {
+    // ServoStyleSets do not need to handle copy-on-write style sheet
+    // innards like with CSSStyleSheets.
+    return;
+  }
+
+  if (!styleSet->EnsureUniqueInnerOnCSSSheets()) {
+    // Nothing to do.
+    return;
+  }
+
+  RebuildAllStyleData(nsChangeHint(0), eRestyle_Subtree);
+}
+
+void
+nsPresContext::FireDOMPaintEvent(nsInvalidateRequestList* aList, uint64_t aTransactionId)
+{
+  nsPIDOMWindowInner* ourWindow = mDocument->GetInnerWindow();
+  if (!ourWindow)
+    return;
+
+  nsCOMPtr<EventTarget> dispatchTarget = do_QueryInterface(ourWindow);
+  nsCOMPtr<EventTarget> eventTarget = dispatchTarget;
+  if (!IsChrome() && !mSendAfterPaintToContent) {
+    // Don't tell the window about this event, it should not know that
+    // something happened in a subdocument. Tell only the chrome event handler.
+    // (Events sent to the window get propagated to the chrome event handler
+    // automatically.)
+    dispatchTarget = do_QueryInterface(ourWindow->GetParentTarget());
+    if (!dispatchTarget) {
+      return;
+    }
+  }
+  // Events sent to the window get propagated to the chrome event handler
+  // automatically.
+  //
+  // This will empty our list in case dispatching the event causes more damage
+  // (hopefully it won't, or we're likely to get an infinite loop! At least
+  // it won't be blocking app execution though).
+  RefPtr<NotifyPaintEvent> event =
+    NS_NewDOMNotifyPaintEvent(eventTarget, this, nullptr, eAfterPaint, aList, aTransactionId);
+
+  // Even if we're not telling the window about the event (so eventTarget is
+  // the chrome event handler, not the window), the window is still
+  // logically the event target.
+  event->SetTarget(eventTarget);
+  event->SetTrusted(true);
+  EventDispatcher::DispatchDOMEvent(dispatchTarget, nullptr,
+                                    static_cast<Event*>(event), this, nullptr);
+}
+
+static bool
+MayHavePaintEventListenerSubdocumentCallback(nsIDocument* aDocument, void* aData)
+{
+  bool *result = static_cast<bool*>(aData);
+  nsIPresShell* shell = aDocument->GetShell();
+  if (shell) {
+    nsPresContext* pc = shell->GetPresContext();
+    if (pc) {
+      *result = pc->MayHavePaintEventListenerInSubDocument();
+
+      // If we found a paint event listener, then we can stop enumerating
+      // sub documents.
+      return !*result;
+    }
+  }
+  return true;
+}
+
+static bool
+MayHavePaintEventListener(nsPIDOMWindowInner* aInnerWindow)
+{
+  if (!aInnerWindow)
+    return false;
+  if (aInnerWindow->HasPaintEventListeners())
+    return true;
+
+  EventTarget* parentTarget = aInnerWindow->GetParentTarget();
+  if (!parentTarget)
+    return false;
+
+  EventListenerManager* manager = nullptr;
+  if ((manager = parentTarget->GetExistingListenerManager()) &&
+      manager->MayHavePaintEventListener()) {
+    return true;
+  }
+
+  nsCOMPtr<nsINode> node;
+  if (parentTarget != aInnerWindow->GetChromeEventHandler()) {
+    nsCOMPtr<nsIInProcessContentFrameMessageManager> mm =
+      do_QueryInterface(parentTarget);
+    if (mm) {
+      node = mm->GetOwnerContent();
+    }
+  }
+
+  if (!node) {
+    node = do_QueryInterface(parentTarget);
+  }
+  if (node)
+    return MayHavePaintEventListener(node->OwnerDoc()->GetInnerWindow());
+
+  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(parentTarget);
+  if (window)
+    return MayHavePaintEventListener(window);
+
+  nsCOMPtr<nsPIWindowRoot> root = do_QueryInterface(parentTarget);
+  EventTarget* tabChildGlobal;
+  return root &&
+         (tabChildGlobal = root->GetParentTarget()) &&
+         (manager = tabChildGlobal->GetExistingListenerManager()) &&
+         manager->MayHavePaintEventListener();
+}
+
+bool
+nsPresContext::MayHavePaintEventListener()
+{
+  return ::MayHavePaintEventListener(mDocument->GetInnerWindow());
+}
+
+bool
+nsPresContext::MayHavePaintEventListenerInSubDocument()
+{
+  if (MayHavePaintEventListener()) {
+    return true;
+  }
+
+  bool result = false;
+  mDocument->EnumerateSubDocuments(MayHavePaintEventListenerSubdocumentCallback, &result);
+  return result;
+}
+
+void
+nsPresContext::NotifyInvalidation(uint32_t aFlags)
+{
+  nsIFrame* rootFrame = PresShell()->FrameManager()->GetRootFrame();
+  NotifyInvalidation(rootFrame->GetVisualOverflowRect(), aFlags);
+  mAllInvalidated = true;
+}
+
+void
+nsPresContext::NotifyInvalidation(const nsIntRect& aRect, uint32_t aFlags)
+{
+  // Prevent values from overflow after DevPixelsToAppUnits().
+  //
+  // DevPixelsTopAppUnits() will multiple a factor (60) to the value,
+  // it may make the result value over the edge (overflow) of max or
+  // min value of int32_t. Compute the max sized dev pixel rect that
+  // we can support and intersect with it.
+  nsIntRect clampedRect = nsIntRect::MaxIntRect();
+  clampedRect.ScaleInverseRoundIn(AppUnitsPerDevPixel());
+
+  clampedRect = clampedRect.Intersect(aRect);
+
+  nsRect rect(DevPixelsToAppUnits(clampedRect.x),
+              DevPixelsToAppUnits(clampedRect.y),
+              DevPixelsToAppUnits(clampedRect.width),
+              DevPixelsToAppUnits(clampedRect.height));
+  NotifyInvalidation(rect, aFlags);
+}
+
+void
+nsPresContext::NotifyInvalidation(const nsRect& aRect, uint32_t aFlags)
+{
+  MOZ_ASSERT(GetContainerWeak(), "Invalidation in detached pres context");
+
+  // If there is no paint event listener, then we don't need to fire
+  // the asynchronous event. We don't even need to record invalidation.
+  // MayHavePaintEventListener is pretty cheap and we could make it
+  // even cheaper by providing a more efficient
+  // nsPIDOMWindow::GetListenerManager.
+
+  if (mAllInvalidated) {
+    return;
+  }
+
+  nsPresContext* pc;
+  for (pc = this; pc; pc = pc->GetParentPresContext()) {
+    if (pc->mFireAfterPaintEvents)
+      break;
+    pc->mFireAfterPaintEvents = true;
+  }
+  if (!pc) {
+    nsRootPresContext* rpc = GetRootPresContext();
+    if (rpc) {
+      rpc->EnsureEventualDidPaintEvent();
+    }
+  }
+
+  nsInvalidateRequestList::Request* request =
+    mInvalidateRequestsSinceLastPaint.mRequests.AppendElement();
+  if (!request)
+    return;
+
+  request->mRect = aRect;
+  request->mFlags = aFlags;
+}
+
+/* static */ void
+nsPresContext::NotifySubDocInvalidation(ContainerLayer* aContainer,
+                                        const nsIntRegion& aRegion)
+{
+  ContainerLayerPresContext *data =
+    static_cast<ContainerLayerPresContext*>(
+      aContainer->GetUserData(&gNotifySubDocInvalidationData));
+  if (!data) {
+    return;
+  }
+
+  nsIntPoint topLeft = aContainer->GetVisibleRegion().ToUnknownRegion().GetBounds().TopLeft();
+
+  for (auto iter = aRegion.RectIter(); !iter.Done(); iter.Next()) {
+    nsIntRect rect(iter.Get());
+    //PresContext coordinate space is relative to the start of our visible
+    // region. Is this really true? This feels like the wrong way to get the right
+    // answer.
+    rect.MoveBy(-topLeft);
+    data->mPresContext->NotifyInvalidation(rect, 0);
+  }
+}
+
+void
+nsPresContext::SetNotifySubDocInvalidationData(ContainerLayer* aContainer)
+{
+  ContainerLayerPresContext* pres = new ContainerLayerPresContext;
+  pres->mPresContext = this;
+  aContainer->SetUserData(&gNotifySubDocInvalidationData, pres);
+}
+
+/* static */ void
+nsPresContext::ClearNotifySubDocInvalidationData(ContainerLayer* aContainer)
+{
+  aContainer->SetUserData(&gNotifySubDocInvalidationData, nullptr);
+}
+
+struct NotifyDidPaintSubdocumentCallbackClosure {
+  uint32_t mFlags;
+  uint64_t mTransactionId;
+  bool mNeedsAnotherDidPaintNotification;
+};
+static bool
+NotifyDidPaintSubdocumentCallback(nsIDocument* aDocument, void* aData)
+{
+  NotifyDidPaintSubdocumentCallbackClosure* closure =
+    static_cast<NotifyDidPaintSubdocumentCallbackClosure*>(aData);
+  nsIPresShell* shell = aDocument->GetShell();
+  if (shell) {
+    nsPresContext* pc = shell->GetPresContext();
+    if (pc) {
+      pc->NotifyDidPaintForSubtree(closure->mFlags, closure->mTransactionId);
+      if (pc->IsDOMPaintEventPending()) {
+        closure->mNeedsAnotherDidPaintNotification = true;
+      }
+    }
+  }
+  return true;
+}
+
+class DelayedFireDOMPaintEvent : public Runnable {
+public:
+  DelayedFireDOMPaintEvent(nsPresContext* aPresContext,
+                           nsInvalidateRequestList* aList,
+                           uint64_t aTransactionId)
+    : mPresContext(aPresContext)
+    , mTransactionId(aTransactionId)
+  {
+    MOZ_ASSERT(mPresContext->GetContainerWeak(),
+               "DOMPaintEvent requested for a detached pres context");
+    mList.TakeFrom(aList);
+  }
+  NS_IMETHOD Run() override
+  {
+    // The pres context might have been detached during the delay -
+    // that's fine, just don't fire the event.
+    if (mPresContext->GetContainerWeak()) {
+      mPresContext->FireDOMPaintEvent(&mList, mTransactionId);
+    }
+    return NS_OK;
+  }
+
+  RefPtr<nsPresContext> mPresContext;
+  uint64_t mTransactionId;
+  nsInvalidateRequestList mList;
+};
+
+void
+nsPresContext::NotifyDidPaintForSubtree(uint32_t aFlags, uint64_t aTransactionId,
+                                        const mozilla::TimeStamp& aTimeStamp)
+{
+  if (IsRoot()) {
+    static_cast<nsRootPresContext*>(this)->CancelDidPaintTimer();
+
+    if (!mFireAfterPaintEvents) {
+      return;
+    }
+  }
+
+  if (!PresShell()->IsVisible() && !mFireAfterPaintEvents) {
+    return;
+  }
+
+  // Non-root prescontexts fire MozAfterPaint to all their descendants
+  // unconditionally, even if no invalidations have been collected. This is
+  // because we don't want to eat the cost of collecting invalidations for
+  // every subdocument (which would require putting every subdocument in its
+  // own layer).
+
+  if (aFlags & nsIPresShell::PAINT_LAYERS) {
+    mUndeliveredInvalidateRequestsBeforeLastPaint.TakeFrom(
+        &mInvalidateRequestsSinceLastPaint);
+    mAllInvalidated = false;
+  }
+  if (aFlags & nsIPresShell::PAINT_COMPOSITE) {
+    nsCOMPtr<nsIRunnable> ev =
+      new DelayedFireDOMPaintEvent(this, &mUndeliveredInvalidateRequestsBeforeLastPaint,
+                                   aTransactionId);
+    nsContentUtils::AddScriptRunner(ev);
+  }
+
+  NotifyDidPaintSubdocumentCallbackClosure closure = { aFlags, aTransactionId, false };
+  mDocument->EnumerateSubDocuments(NotifyDidPaintSubdocumentCallback, &closure);
+
+  if (!closure.mNeedsAnotherDidPaintNotification &&
+      mInvalidateRequestsSinceLastPaint.IsEmpty() &&
+      mUndeliveredInvalidateRequestsBeforeLastPaint.IsEmpty()) {
+    // Nothing more to do for the moment.
+    mFireAfterPaintEvents = false;
+  } else {
+    if (IsRoot()) {
+      static_cast<nsRootPresContext*>(this)->EnsureEventualDidPaintEvent();
+    }
+  }
+}
+
+bool
+nsPresContext::HasCachedStyleData()
+{
+  if (!mShell) {
+    return false;
+  }
+
+  nsStyleSet* styleSet = mShell->StyleSet()->GetAsGecko();
+  if (!styleSet) {
+    // XXXheycam ServoStyleSets do not use the rule tree, so just assume for now
+    // that we need to restyle when e.g. dppx changes assuming we're sufficiently
+    // bootstrapped.
+    return mShell->DidInitialize();
+  }
+
+  return styleSet->HasCachedStyleData();
+}
+
+already_AddRefed<nsITimer>
+nsPresContext::CreateTimer(nsTimerCallbackFunc aCallback,
+                           uint32_t aDelay)
+{
+  nsCOMPtr<nsITimer> timer = do_CreateInstance("@mozilla.org/timer;1");
+  if (timer) {
+    nsresult rv = timer->InitWithFuncCallback(aCallback, this, aDelay,
+                                              nsITimer::TYPE_ONE_SHOT);
+    if (NS_SUCCEEDED(rv)) {
+      return timer.forget();
+    }
+  }
+
+  return nullptr;
+}
+
+static bool sGotInterruptEnv = false;
+enum InterruptMode {
+  ModeRandom,
+  ModeCounter,
+  ModeEvent
+};
+// Controlled by the GECKO_REFLOW_INTERRUPT_MODE env var; allowed values are
+// "random" (except on Windows) or "counter".  If neither is used, the mode is
+// ModeEvent.
+static InterruptMode sInterruptMode = ModeEvent;
+#ifndef XP_WIN
+// Used for the "random" mode.  Controlled by the GECKO_REFLOW_INTERRUPT_SEED
+// env var.
+static uint32_t sInterruptSeed = 1;
+#endif
+// Used for the "counter" mode.  This is the number of unskipped interrupt
+// checks that have to happen before we interrupt.  Controlled by the
+// GECKO_REFLOW_INTERRUPT_FREQUENCY env var.
+static uint32_t sInterruptMaxCounter = 10;
+// Used for the "counter" mode.  This counts up to sInterruptMaxCounter and is
+// then reset to 0.
+static uint32_t sInterruptCounter;
+// Number of interrupt checks to skip before really trying to interrupt.
+// Controlled by the GECKO_REFLOW_INTERRUPT_CHECKS_TO_SKIP env var.
+static uint32_t sInterruptChecksToSkip = 200;
+// Number of milliseconds that a reflow should be allowed to run for before we
+// actually allow interruption.  Controlled by the
+// GECKO_REFLOW_MIN_NOINTERRUPT_DURATION env var.  Can't be initialized here,
+// because TimeDuration/TimeStamp is not safe to use in static constructors..
+static TimeDuration sInterruptTimeout;
+
+static void GetInterruptEnv()
+{
+  char *ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_MODE");
+  if (ev) {
+#ifndef XP_WIN
+    if (PL_strcasecmp(ev, "random") == 0) {
+      ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_SEED");
+      if (ev) {
+        sInterruptSeed = atoi(ev);
+      }
+      srandom(sInterruptSeed);
+      sInterruptMode = ModeRandom;
+    } else
+#endif
+      if (PL_strcasecmp(ev, "counter") == 0) {
+      ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_FREQUENCY");
+      if (ev) {
+        sInterruptMaxCounter = atoi(ev);
+      }
+      sInterruptCounter = 0;
+      sInterruptMode = ModeCounter;
+    }
+  }
+  ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_CHECKS_TO_SKIP");
+  if (ev) {
+    sInterruptChecksToSkip = atoi(ev);
+  }
+
+  ev = PR_GetEnv("GECKO_REFLOW_MIN_NOINTERRUPT_DURATION");
+  int duration_ms = ev ? atoi(ev) : 100;
+  sInterruptTimeout = TimeDuration::FromMilliseconds(duration_ms);
+}
+
+bool
+nsPresContext::HavePendingInputEvent()
+{
+  switch (sInterruptMode) {
+#ifndef XP_WIN
+    case ModeRandom:
+      return (random() & 1);
+#endif
+    case ModeCounter:
+      if (sInterruptCounter < sInterruptMaxCounter) {
+        ++sInterruptCounter;
+        return false;
+      }
+      sInterruptCounter = 0;
+      return true;
+    default:
+    case ModeEvent: {
+      nsIFrame* f = PresShell()->GetRootFrame();
+      if (f) {
+        nsIWidget* w = f->GetNearestWidget();
+        if (w) {
+          return w->HasPendingInputEvent();
+        }
+      }
+      return false;
+    }
+  }
+}
+
+void
+nsPresContext::NotifyFontFaceSetOnRefresh()
+{
+  FontFaceSet* set = mDocument->GetFonts();
+  if (set) {
+    set->DidRefresh();
+  }
+}
+
+bool
+nsPresContext::HasPendingRestyleOrReflow()
+{
+  return (mRestyleManager && mRestyleManager->HasPendingRestyles()) ||
+         PresShell()->HasPendingReflow();
+}
+
+void
+nsPresContext::ReflowStarted(bool aInterruptible)
+{
+#ifdef NOISY_INTERRUPTIBLE_REFLOW
+  if (!aInterruptible) {
+    printf("STARTING NONINTERRUPTIBLE REFLOW\n");
+  }
+#endif
+  // We don't support interrupting in paginated contexts, since page
+  // sequences only handle initial reflow
+  mInterruptsEnabled = aInterruptible && !IsPaginated() &&
+                       nsLayoutUtils::InterruptibleReflowEnabled();
+
+  // Don't set mHasPendingInterrupt based on HavePendingInputEvent() here.  If
+  // we ever change that, then we need to update the code in
+  // PresShell::DoReflow to only add the just-reflown root to dirty roots if
+  // it's actually dirty.  Otherwise we can end up adding a root that has no
+  // interruptible descendants, just because we detected an interrupt at reflow
+  // start.
+  mHasPendingInterrupt = false;
+
+  mInterruptChecksToSkip = sInterruptChecksToSkip;
+
+  if (mInterruptsEnabled) {
+    mReflowStartTime = TimeStamp::Now();
+  }
+}
+
+bool
+nsPresContext::CheckForInterrupt(nsIFrame* aFrame)
+{
+  if (mHasPendingInterrupt) {
+    mShell->FrameNeedsToContinueReflow(aFrame);
+    return true;
+  }
+
+  if (!sGotInterruptEnv) {
+    sGotInterruptEnv = true;
+    GetInterruptEnv();
+  }
+
+  if (!mInterruptsEnabled) {
+    return false;
+  }
+
+  if (mInterruptChecksToSkip > 0) {
+    --mInterruptChecksToSkip;
+    return false;
+  }
+  mInterruptChecksToSkip = sInterruptChecksToSkip;
+
+  // Don't interrupt if it's been less than sInterruptTimeout since we started
+  // the reflow.
+  mHasPendingInterrupt =
+    TimeStamp::Now() - mReflowStartTime > sInterruptTimeout &&
+    HavePendingInputEvent() &&
+    !IsChrome();
+
+  if (mPendingInterruptFromTest) {
+    mPendingInterruptFromTest = false;
+    mHasPendingInterrupt = true;
+  }
+
+  if (mHasPendingInterrupt) {
+#ifdef NOISY_INTERRUPTIBLE_REFLOW
+    printf("*** DETECTED pending interrupt (time=%lld)\n", PR_Now());
+#endif /* NOISY_INTERRUPTIBLE_REFLOW */
+    mShell->FrameNeedsToContinueReflow(aFrame);
+  }
+  return mHasPendingInterrupt;
+}
+
+nsIFrame*
+nsPresContext::GetPrimaryFrameFor(nsIContent* aContent)
+{
+  NS_PRECONDITION(aContent, "Don't do that");
+  if (GetPresShell() &&
+      GetPresShell()->GetDocument() == aContent->GetComposedDoc()) {
+    return aContent->GetPrimaryFrame();
+  }
+  return nullptr;
+}
+
+size_t
+nsPresContext::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
+{
+  return mPropertyTable.SizeOfExcludingThis(aMallocSizeOf) +
+         mLangGroupFontPrefs.SizeOfExcludingThis(aMallocSizeOf);
+
+  // Measurement of other members may be added later if DMD finds it is
+  // worthwhile.
+}
+
+bool
+nsPresContext::IsRootContentDocument() const
+{
+  // We are a root content document if: we are not a resource doc, we are
+  // not chrome, and we either have no parent or our parent is chrome.
+  if (mDocument->IsResourceDoc()) {
+    return false;
+  }
+  if (IsChrome()) {
+    return false;
+  }
+  // We may not have a root frame, so use views.
+  nsView* view = PresShell()->GetViewManager()->GetRootView();
+  if (!view) {
+    return false;
+  }
+  view = view->GetParent(); // anonymous inner view
+  if (!view) {
+    return true;
+  }
+  view = view->GetParent(); // subdocumentframe's view
+  if (!view) {
+    return true;
+  }
+
+  nsIFrame* f = view->GetFrame();
+  return (f && f->PresContext()->IsChrome());
+}
+
+void
+nsPresContext::NotifyNonBlankPaint()
+{
+  MOZ_ASSERT(!mHadNonBlankPaint);
+  mHadNonBlankPaint = true;
+  if (IsRootContentDocument()) {
+    RefPtr<nsDOMNavigationTiming> timing = mDocument->GetNavigationTiming();
+    if (timing) {
+      timing->NotifyNonBlankPaintForRootContentDocument();
+    }
+  }
+}
+
+bool nsPresContext::GetPaintFlashing() const
+{
+  if (!mPaintFlashingInitialized) {
+    bool pref = Preferences::GetBool("nglayout.debug.paint_flashing");
+    if (!pref && IsChrome()) {
+      pref = Preferences::GetBool("nglayout.debug.paint_flashing_chrome");
+    }
+    mPaintFlashing = pref;
+    mPaintFlashingInitialized = true;
+  }
+  return mPaintFlashing;
+}
+
+int32_t
+nsPresContext::AppUnitsPerDevPixel() const
+{
+  return mDeviceContext->AppUnitsPerDevPixel();
+}
+
+nscoord
+nsPresContext::GfxUnitsToAppUnits(gfxFloat aGfxUnits) const
+{
+  return mDeviceContext->GfxUnitsToAppUnits(aGfxUnits);
+}
+
+gfxFloat
+nsPresContext::AppUnitsToGfxUnits(nscoord aAppUnits) const
+{
+  return mDeviceContext->AppUnitsToGfxUnits(aAppUnits);
+}
+
+bool
+nsPresContext::IsDeviceSizePageSize()
+{
+  bool isDeviceSizePageSize = false;
+  nsCOMPtr<nsIDocShell> docShell(mContainer);
+  if (docShell) {
+    isDeviceSizePageSize = docShell->GetDeviceSizeIsPageSize();
+  }
+  return isDeviceSizePageSize;
+}
+
+uint64_t
+nsPresContext::GetRestyleGeneration() const
+{
+  if (!mRestyleManager) {
+    return 0;
+  }
+  return mRestyleManager->GetRestyleGeneration();
+}
+
+nsRootPresContext::nsRootPresContext(nsIDocument* aDocument,
+                                     nsPresContextType aType)
+  : nsPresContext(aDocument, aType),
+    mDOMGeneration(0)
+{
+}
+
+nsRootPresContext::~nsRootPresContext()
+{
+  NS_ASSERTION(mRegisteredPlugins.Count() == 0,
+               "All plugins should have been unregistered");
+  CancelDidPaintTimer();
+  CancelApplyPluginGeometryTimer();
+}
+
+/* virtual */ void
+nsRootPresContext::Detach()
+{
+  CancelDidPaintTimer();
+  // XXXmats maybe also CancelApplyPluginGeometryTimer(); ?
+  nsPresContext::Detach();
+}
+
+void
+nsRootPresContext::RegisterPluginForGeometryUpdates(nsIContent* aPlugin)
+{
+  mRegisteredPlugins.PutEntry(aPlugin);
+}
+
+void
+nsRootPresContext::UnregisterPluginForGeometryUpdates(nsIContent* aPlugin)
+{
+  mRegisteredPlugins.RemoveEntry(aPlugin);
+}
+
+void
+nsRootPresContext::ComputePluginGeometryUpdates(nsIFrame* aFrame,
+                                                nsDisplayListBuilder* aBuilder,
+                                                nsDisplayList* aList)
+{
+  if (mRegisteredPlugins.Count() == 0) {
+    return;
+  }
+
+  // Initially make the next state for each plugin descendant of aFrame be
+  // "hidden". Plugins that are visible will have their next state set to
+  // unhidden by nsDisplayPlugin::ComputeVisibility.
+  for (auto iter = mRegisteredPlugins.Iter(); !iter.Done(); iter.Next()) {
+    auto f = static_cast<nsPluginFrame*>(iter.Get()->GetKey()->GetPrimaryFrame());
+    if (!f) {
+      NS_WARNING("Null frame in ComputePluginGeometryUpdates");
+      continue;
+    }
+    if (!nsLayoutUtils::IsAncestorFrameCrossDoc(aFrame, f)) {
+      // f is not managed by this frame so we should ignore it.
+      continue;
+    }
+    f->SetEmptyWidgetConfiguration();
+  }
+
+  nsIFrame* rootFrame = FrameManager()->GetRootFrame();
+
+  if (rootFrame && aBuilder->ContainsPluginItem()) {
+    aBuilder->SetForPluginGeometry();
+    aBuilder->SetAccurateVisibleRegions();
+    // Merging and flattening has already been done and we should not do it
+    // again. nsDisplayScroll(Info)Layer doesn't support trying to flatten
+    // again.
+    aBuilder->SetAllowMergingAndFlattening(false);
+    nsRegion region = rootFrame->GetVisualOverflowRectRelativeToSelf();
+    // nsDisplayPlugin::ComputeVisibility will automatically set a non-hidden
+    // widget configuration for the plugin, if it's visible.
+    aList->ComputeVisibilityForRoot(aBuilder, &region);
+  }
+
+#ifdef XP_MACOSX
+  // We control painting of Mac plugins, so just apply geometry updates now.
+  // This is not happening during a paint event.
+  ApplyPluginGeometryUpdates();
+#else
+  if (XRE_IsParentProcess()) {
+    InitApplyPluginGeometryTimer();
+  }
+#endif
+}
+
+static void
+ApplyPluginGeometryUpdatesCallback(nsITimer *aTimer, void *aClosure)
+{
+  static_cast<nsRootPresContext*>(aClosure)->ApplyPluginGeometryUpdates();
+}
+
+void
+nsRootPresContext::InitApplyPluginGeometryTimer()
+{
+  if (mApplyPluginGeometryTimer) {
+    return;
+  }
+
+  // We'll apply the plugin geometry updates during the next compositing paint in this
+  // presContext (either from nsPresShell::WillPaintWindow or from
+  // nsPresShell::DidPaintWindow, depending on the platform).  But paints might
+  // get optimized away if the old plugin geometry covers the invalid region,
+  // so set a backup timer to do this too.  We want to make sure this
+  // won't fire before our normal paint notifications, if those would
+  // update the geometry, so set it for double the refresh driver interval.
+  mApplyPluginGeometryTimer = CreateTimer(ApplyPluginGeometryUpdatesCallback,
+                                          nsRefreshDriver::DefaultInterval() * 2);
+}
+
+void
+nsRootPresContext::CancelApplyPluginGeometryTimer()
+{
+  if (mApplyPluginGeometryTimer) {
+    mApplyPluginGeometryTimer->Cancel();
+    mApplyPluginGeometryTimer = nullptr;
+  }
+}
+
+#ifndef XP_MACOSX
+
+static bool
+HasOverlap(const LayoutDeviceIntPoint& aOffset1,
+           const nsTArray<LayoutDeviceIntRect>& aClipRects1,
+           const LayoutDeviceIntPoint& aOffset2,
+           const nsTArray<LayoutDeviceIntRect>& aClipRects2)
+{
+  LayoutDeviceIntPoint offsetDelta = aOffset1 - aOffset2;
+  for (uint32_t i = 0; i < aClipRects1.Length(); ++i) {
+    for (uint32_t j = 0; j < aClipRects2.Length(); ++j) {
+      if ((aClipRects1[i] + offsetDelta).Intersects(aClipRects2[j])) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+/**
+ * Given a list of plugin windows to move to new locations, sort the list
+ * so that for each window move, the window moves to a location that
+ * does not intersect other windows. This minimizes flicker and repainting.
+ * It's not always possible to do this perfectly, since in general
+ * we might have cycles. But we do our best.
+ * We need to take into account that windows are clipped to particular
+ * regions and the clip regions change as the windows are moved.
+ */
+static void
+SortConfigurations(nsTArray<nsIWidget::Configuration>* aConfigurations)
+{
+  if (aConfigurations->Length() > 10) {
+    // Give up, we don't want to get bogged down here
+    return;
+  }
+
+  nsTArray<nsIWidget::Configuration> pluginsToMove;
+  pluginsToMove.SwapElements(*aConfigurations);
+
+  // Our algorithm is quite naive. At each step we try to identify
+  // a window that can be moved to its new location that won't overlap
+  // any other windows at the new location. If there is no such
+  // window, we just move the last window in the list anyway.
+  while (!pluginsToMove.IsEmpty()) {
+    // Find a window whose destination does not overlap any other window
+    uint32_t i;
+    for (i = 0; i + 1 < pluginsToMove.Length(); ++i) {
+      nsIWidget::Configuration* config = &pluginsToMove[i];
+      bool foundOverlap = false;
+      for (uint32_t j = 0; j < pluginsToMove.Length(); ++j) {
+        if (i == j)
+          continue;
+        LayoutDeviceIntRect bounds = pluginsToMove[j].mChild->GetBounds();
+        AutoTArray<LayoutDeviceIntRect,1> clipRects;
+        pluginsToMove[j].mChild->GetWindowClipRegion(&clipRects);
+        if (HasOverlap(bounds.TopLeft(), clipRects,
+                       config->mBounds.TopLeft(),
+                       config->mClipRegion)) {
+          foundOverlap = true;
+          break;
+        }
+      }
+      if (!foundOverlap)
+        break;
+    }
+    // Note that we always move the last plugin in pluginsToMove, if we
+    // can't find any other plugin to move
+    aConfigurations->AppendElement(pluginsToMove[i]);
+    pluginsToMove.RemoveElementAt(i);
+  }
+}
+
+static void
+PluginGetGeometryUpdate(nsTHashtable<nsRefPtrHashKey<nsIContent>>& aPlugins,
+                        nsTArray<nsIWidget::Configuration>* aConfigurations)
+{
+  for (auto iter = aPlugins.Iter(); !iter.Done(); iter.Next()) {
+    auto f = static_cast<nsPluginFrame*>(iter.Get()->GetKey()->GetPrimaryFrame());
+    if (!f) {
+      NS_WARNING("Null frame in PluginGeometryUpdate");
+      continue;
+    }
+    f->GetWidgetConfiguration(aConfigurations);
+  }
+}
+
+#endif  // #ifndef XP_MACOSX
+
+static void
+PluginDidSetGeometry(nsTHashtable<nsRefPtrHashKey<nsIContent>>& aPlugins)
+{
+  for (auto iter = aPlugins.Iter(); !iter.Done(); iter.Next()) {
+    auto f = static_cast<nsPluginFrame*>(iter.Get()->GetKey()->GetPrimaryFrame());
+    if (!f) {
+      NS_WARNING("Null frame in PluginDidSetGeometry");
+      continue;
+    }
+    f->DidSetWidgetGeometry();
+  }
+}
+
+void
+nsRootPresContext::ApplyPluginGeometryUpdates()
+{
+#ifndef XP_MACOSX
+  CancelApplyPluginGeometryTimer();
+
+  nsTArray<nsIWidget::Configuration> configurations;
+  PluginGetGeometryUpdate(mRegisteredPlugins, &configurations);
+  // Walk mRegisteredPlugins and ask each plugin for its configuration
+  if (!configurations.IsEmpty()) {
+    nsIWidget* widget = configurations[0].mChild->GetParent();
+    NS_ASSERTION(widget, "Plugins must have a parent window");
+    SortConfigurations(&configurations);
+    widget->ConfigureChildren(configurations);
+  }
+#endif  // #ifndef XP_MACOSX
+
+  PluginDidSetGeometry(mRegisteredPlugins);
+}
+
+void
+nsRootPresContext::CollectPluginGeometryUpdates(LayerManager* aLayerManager)
+{
+#ifndef XP_MACOSX
+  // Collect and pass plugin widget configurations down to the compositor
+  // for transmission to the chrome process.
+  NS_ASSERTION(aLayerManager, "layer manager is invalid!");
+  mozilla::layers::ClientLayerManager* clm = aLayerManager->AsClientLayerManager();
+
+  nsTArray<nsIWidget::Configuration> configurations;
+  // If there aren't any plugins to configure, clear the plugin data cache
+  // in the layer system.
+  if (!mRegisteredPlugins.Count() && clm) {
+    clm->StorePluginWidgetConfigurations(configurations);
+    return;
+  }
+  PluginGetGeometryUpdate(mRegisteredPlugins, &configurations);
+  if (configurations.IsEmpty()) {
+    PluginDidSetGeometry(mRegisteredPlugins);
+    return;
+  }
+  SortConfigurations(&configurations);
+  if (clm) {
+    clm->StorePluginWidgetConfigurations(configurations);
+  }
+  PluginDidSetGeometry(mRegisteredPlugins);
+#endif  // #ifndef XP_MACOSX
+}
+
+static void
+NotifyDidPaintForSubtreeCallback(nsITimer *aTimer, void *aClosure)
+{
+  nsPresContext* presContext = (nsPresContext*)aClosure;
+  nsAutoScriptBlocker blockScripts;
+  // This is a fallback if we don't get paint events for some reason
+  // so we'll just pretend both layer painting and compositing happened.
+  presContext->NotifyDidPaintForSubtree(
+      nsIPresShell::PAINT_LAYERS | nsIPresShell::PAINT_COMPOSITE);
+}
+
+void
+nsRootPresContext::EnsureEventualDidPaintEvent()
+{
+  if (mNotifyDidPaintTimer)
+    return;
+
+  mNotifyDidPaintTimer = CreateTimer(NotifyDidPaintForSubtreeCallback, 100);
+}
+
+void
+nsRootPresContext::AddWillPaintObserver(nsIRunnable* aRunnable)
+{
+  if (!mWillPaintFallbackEvent.IsPending()) {
+    mWillPaintFallbackEvent = new RunWillPaintObservers(this);
+    NS_DispatchToMainThread(mWillPaintFallbackEvent.get());
+  }
+  mWillPaintObservers.AppendElement(aRunnable);
+}
+
+/**
+ * Run all runnables that need to get called before the next paint.
+ */
+void
+nsRootPresContext::FlushWillPaintObservers()
+{
+  mWillPaintFallbackEvent = nullptr;
+  nsTArray<nsCOMPtr<nsIRunnable> > observers;
+  observers.SwapElements(mWillPaintObservers);
+  for (uint32_t i = 0; i < observers.Length(); ++i) {
+    observers[i]->Run();
+  }
+}
+
+size_t
+nsRootPresContext::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
+{
+  return nsPresContext::SizeOfExcludingThis(aMallocSizeOf);
+
+  // Measurement of the following members may be added later if DMD finds it is
+  // worthwhile:
+  // - mNotifyDidPaintTimer
+  // - mRegisteredPlugins
+  // - mWillPaintObservers
+  // - mWillPaintFallbackEvent
+}