Add m-esr52 at 52.6.0

1 files changed, 6138 insertions, 0 deletions

diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
new file mode 100644
index 000000000..1c6d97395
--- /dev/null
+++ b/layout/base/nsCSSRendering.cpp
@@ -0,0 +1,6138 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+// vim:cindent:ts=2:et:sw=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/. */
+
+/* utility functions for drawing borders and backgrounds */
+
+#include <ctime>
+
+#include "gfx2DGlue.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Helpers.h"
+#include "mozilla/gfx/PathHelpers.h"
+#include "mozilla/HashFunctions.h"
+#include "mozilla/MathAlgorithms.h"
+
+#include "BorderConsts.h"
+#include "nsISVGChildFrame.h"
+#include "nsStyleConsts.h"
+#include "nsPresContext.h"
+#include "nsIFrame.h"
+#include "nsPoint.h"
+#include "nsRect.h"
+#include "nsIPresShell.h"
+#include "nsFrameManager.h"
+#include "nsStyleContext.h"
+#include "nsGkAtoms.h"
+#include "nsCSSAnonBoxes.h"
+#include "nsIContent.h"
+#include "nsIDocumentInlines.h"
+#include "nsIScrollableFrame.h"
+#include "imgIRequest.h"
+#include "imgIContainer.h"
+#include "ImageOps.h"
+#include "nsCSSRendering.h"
+#include "nsCSSColorUtils.h"
+#include "nsITheme.h"
+#include "nsThemeConstants.h"
+#include "nsLayoutUtils.h"
+#include "nsBlockFrame.h"
+#include "gfxContext.h"
+#include "nsRenderingContext.h"
+#include "nsStyleStructInlines.h"
+#include "nsCSSFrameConstructor.h"
+#include "nsCSSProps.h"
+#include "nsContentUtils.h"
+#include "nsSVGEffects.h"
+#include "nsSVGIntegrationUtils.h"
+#include "gfxDrawable.h"
+#include "GeckoProfiler.h"
+#include "nsCSSRenderingBorders.h"
+#include "mozilla/css/ImageLoader.h"
+#include "ImageContainer.h"
+#include "mozilla/Telemetry.h"
+#include "gfxUtils.h"
+#include "gfxGradientCache.h"
+#include "nsInlineFrame.h"
+#include "nsRubyTextContainerFrame.h"
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::css;
+using namespace mozilla::gfx;
+using namespace mozilla::image;
+using mozilla::CSSSizeOrRatio;
+
+static int gFrameTreeLockCount = 0;
+
+// To avoid storing this data on nsInlineFrame (bloat) and to avoid
+// recalculating this for each frame in a continuation (perf), hold
+// a cache of various coordinate information that we need in order
+// to paint inline backgrounds.
+struct InlineBackgroundData
+{
+  InlineBackgroundData()
+      : mFrame(nullptr), mLineContainer(nullptr)
+  {
+  }
+
+  ~InlineBackgroundData()
+  {
+  }
+
+  void Reset()
+  {
+    mBoundingBox.SetRect(0,0,0,0);
+    mContinuationPoint = mLineContinuationPoint = mUnbrokenMeasure = 0;
+    mFrame = mLineContainer = nullptr;
+    mPIStartBorderData.Reset();
+  }
+
+  /**
+   * Return a continuous rect for (an inline) aFrame relative to the
+   * continuation that draws the left-most part of the background.
+   * This is used when painting backgrounds.
+   */
+  nsRect GetContinuousRect(nsIFrame* aFrame)
+  {
+    MOZ_ASSERT(static_cast<nsInlineFrame*>(do_QueryFrame(aFrame)));
+
+    SetFrame(aFrame);
+
+    nscoord pos; // an x coordinate if writing-mode is horizontal;
+                 // y coordinate if vertical
+    if (mBidiEnabled) {
+      pos = mLineContinuationPoint;
+
+      // Scan continuations on the same line as aFrame and accumulate the widths
+      // of frames that are to the left (if this is an LTR block) or right
+      // (if it's RTL) of the current one.
+      bool isRtlBlock = (mLineContainer->StyleVisibility()->mDirection ==
+                           NS_STYLE_DIRECTION_RTL);
+      nscoord curOffset = mVertical ? aFrame->GetOffsetTo(mLineContainer).y
+                                    : aFrame->GetOffsetTo(mLineContainer).x;
+
+      // If the continuation is fluid we know inlineFrame is not on the same line.
+      // If it's not fluid, we need to test further to be sure.
+      nsIFrame* inlineFrame = aFrame->GetPrevContinuation();
+      while (inlineFrame && !inlineFrame->GetNextInFlow() &&
+             AreOnSameLine(aFrame, inlineFrame)) {
+        nscoord frameOffset = mVertical
+          ? inlineFrame->GetOffsetTo(mLineContainer).y
+          : inlineFrame->GetOffsetTo(mLineContainer).x;
+        if (isRtlBlock == (frameOffset >= curOffset)) {
+          pos += mVertical
+               ? inlineFrame->GetSize().height
+               : inlineFrame->GetSize().width;
+        }
+        inlineFrame = inlineFrame->GetPrevContinuation();
+      }
+
+      inlineFrame = aFrame->GetNextContinuation();
+      while (inlineFrame && !inlineFrame->GetPrevInFlow() &&
+             AreOnSameLine(aFrame, inlineFrame)) {
+        nscoord frameOffset = mVertical
+          ? inlineFrame->GetOffsetTo(mLineContainer).y
+          : inlineFrame->GetOffsetTo(mLineContainer).x;
+        if (isRtlBlock == (frameOffset >= curOffset)) {
+          pos += mVertical
+                 ? inlineFrame->GetSize().height
+                 : inlineFrame->GetSize().width;
+        }
+        inlineFrame = inlineFrame->GetNextContinuation();
+      }
+      if (isRtlBlock) {
+        // aFrame itself is also to the right of its left edge, so add its width.
+        pos += mVertical ? aFrame->GetSize().height : aFrame->GetSize().width;
+        // pos is now the distance from the left [top] edge of aFrame to the right [bottom] edge
+        // of the unbroken content. Change it to indicate the distance from the
+        // left [top] edge of the unbroken content to the left [top] edge of aFrame.
+        pos = mUnbrokenMeasure - pos;
+      }
+    } else {
+      pos = mContinuationPoint;
+    }
+
+    // Assume background-origin: border and return a rect with offsets
+    // relative to (0,0).  If we have a different background-origin,
+    // then our rect should be deflated appropriately by our caller.
+    return mVertical
+      ? nsRect(0, -pos, mFrame->GetSize().width, mUnbrokenMeasure)
+      : nsRect(-pos, 0, mUnbrokenMeasure, mFrame->GetSize().height);
+  }
+
+  /**
+   * Return a continuous rect for (an inline) aFrame relative to the
+   * continuation that should draw the left[top]-border.  This is used when painting
+   * borders and clipping backgrounds.  This may NOT be the same continuous rect
+   * as for drawing backgrounds; the continuation with the left[top]-border might be
+   * somewhere in the middle of that rect (e.g. BIDI), in those cases we need
+   * the reverse background order starting at the left[top]-border continuation.
+   */
+  nsRect GetBorderContinuousRect(nsIFrame* aFrame, nsRect aBorderArea)
+  {
+    // Calling GetContinuousRect(aFrame) here may lead to Reset/Init which
+    // resets our mPIStartBorderData so we save it ...
+    PhysicalInlineStartBorderData saved(mPIStartBorderData);
+    nsRect joinedBorderArea = GetContinuousRect(aFrame);
+    if (!saved.mIsValid || saved.mFrame != mPIStartBorderData.mFrame) {
+      if (aFrame == mPIStartBorderData.mFrame) {
+        if (mVertical) {
+          mPIStartBorderData.SetCoord(joinedBorderArea.y);
+        } else {
+          mPIStartBorderData.SetCoord(joinedBorderArea.x);
+        }
+      } else if (mPIStartBorderData.mFrame) {
+        if (mVertical) {
+          mPIStartBorderData.SetCoord(GetContinuousRect(mPIStartBorderData.mFrame).y);
+        } else {
+          mPIStartBorderData.SetCoord(GetContinuousRect(mPIStartBorderData.mFrame).x);
+        }
+      }
+    } else {
+      // ... and restore it when possible.
+      mPIStartBorderData.mCoord = saved.mCoord;
+    }
+    if (mVertical) {
+      if (joinedBorderArea.y > mPIStartBorderData.mCoord) {
+        joinedBorderArea.y =
+          -(mUnbrokenMeasure + joinedBorderArea.y - aBorderArea.height);
+      } else {
+        joinedBorderArea.y -= mPIStartBorderData.mCoord;
+      }
+    } else {
+      if (joinedBorderArea.x > mPIStartBorderData.mCoord) {
+        joinedBorderArea.x =
+          -(mUnbrokenMeasure + joinedBorderArea.x - aBorderArea.width);
+      } else {
+        joinedBorderArea.x -= mPIStartBorderData.mCoord;
+      }
+    }
+    return joinedBorderArea;
+  }
+
+  nsRect GetBoundingRect(nsIFrame* aFrame)
+  {
+    SetFrame(aFrame);
+
+    // Move the offsets relative to (0,0) which puts the bounding box into
+    // our coordinate system rather than our parent's.  We do this by
+    // moving it the back distance from us to the bounding box.
+    // This also assumes background-origin: border, so our caller will
+    // need to deflate us if needed.
+    nsRect boundingBox(mBoundingBox);
+    nsPoint point = mFrame->GetPosition();
+    boundingBox.MoveBy(-point.x, -point.y);
+
+    return boundingBox;
+  }
+
+protected:
+  // This is a coordinate on the inline axis, but is not a true logical inline-
+  // coord because it is always measured from left to right (if horizontal) or
+  // from top to bottom (if vertical), ignoring any bidi RTL directionality.
+  // We'll call this "physical inline start", or PIStart for short.
+  struct PhysicalInlineStartBorderData {
+    nsIFrame* mFrame;   // the continuation that may have a left-border
+    nscoord   mCoord;   // cached GetContinuousRect(mFrame).x or .y
+    bool      mIsValid; // true if mCoord is valid
+    void Reset() { mFrame = nullptr; mIsValid = false; }
+    void SetCoord(nscoord aCoord) { mCoord = aCoord; mIsValid = true; }
+  };
+
+  nsIFrame*      mFrame;
+  nsIFrame*      mLineContainer;
+  nsRect         mBoundingBox;
+  nscoord        mContinuationPoint;
+  nscoord        mUnbrokenMeasure;
+  nscoord        mLineContinuationPoint;
+  PhysicalInlineStartBorderData mPIStartBorderData;
+  bool           mBidiEnabled;
+  bool           mVertical;
+
+  void SetFrame(nsIFrame* aFrame)
+  {
+    NS_PRECONDITION(aFrame, "Need a frame");
+    NS_ASSERTION(gFrameTreeLockCount > 0,
+                 "Can't call this when frame tree is not locked");
+
+    if (aFrame == mFrame) {
+      return;
+    }
+
+    nsIFrame *prevContinuation = GetPrevContinuation(aFrame);
+
+    if (!prevContinuation || mFrame != prevContinuation) {
+      // Ok, we've got the wrong frame.  We have to start from scratch.
+      Reset();
+      Init(aFrame);
+      return;
+    }
+
+    // Get our last frame's size and add its width to our continuation
+    // point before we cache the new frame.
+    mContinuationPoint += mVertical ? mFrame->GetSize().height
+                                    : mFrame->GetSize().width;
+
+    // If this a new line, update mLineContinuationPoint.
+    if (mBidiEnabled &&
+        (aFrame->GetPrevInFlow() || !AreOnSameLine(mFrame, aFrame))) {
+       mLineContinuationPoint = mContinuationPoint;
+    }
+
+    mFrame = aFrame;
+  }
+
+  nsIFrame* GetPrevContinuation(nsIFrame* aFrame)
+  {
+    nsIFrame* prevCont = aFrame->GetPrevContinuation();
+    if (!prevCont &&
+        (aFrame->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT)) {
+      nsIFrame* block =
+        aFrame->Properties().Get(nsIFrame::IBSplitPrevSibling());
+      if (block) {
+        // The {ib} properties are only stored on first continuations
+        NS_ASSERTION(!block->GetPrevContinuation(),
+                     "Incorrect value for IBSplitPrevSibling");
+        prevCont =
+          block->Properties().Get(nsIFrame::IBSplitPrevSibling());
+        NS_ASSERTION(prevCont, "How did that happen?");
+      }
+    }
+    return prevCont;
+  }
+
+  nsIFrame* GetNextContinuation(nsIFrame* aFrame)
+  {
+    nsIFrame* nextCont = aFrame->GetNextContinuation();
+    if (!nextCont &&
+        (aFrame->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT)) {
+      // The {ib} properties are only stored on first continuations
+      aFrame = aFrame->FirstContinuation();
+      nsIFrame* block = aFrame->Properties().Get(nsIFrame::IBSplitSibling());
+      if (block) {
+        nextCont = block->Properties().Get(nsIFrame::IBSplitSibling());
+        NS_ASSERTION(nextCont, "How did that happen?");
+      }
+    }
+    return nextCont;
+  }
+
+  void Init(nsIFrame* aFrame)
+  {
+    mPIStartBorderData.Reset();
+    mBidiEnabled = aFrame->PresContext()->BidiEnabled();
+    if (mBidiEnabled) {
+      // Find the line container frame
+      mLineContainer = aFrame;
+      while (mLineContainer &&
+             mLineContainer->IsFrameOfType(nsIFrame::eLineParticipant)) {
+        mLineContainer = mLineContainer->GetParent();
+      }
+
+      MOZ_ASSERT(mLineContainer, "Cannot find line containing frame.");
+      MOZ_ASSERT(mLineContainer != aFrame, "line container frame "
+                 "should be an ancestor of the target frame.");
+    }
+
+    mVertical = aFrame->GetWritingMode().IsVertical();
+
+    // Start with the previous flow frame as our continuation point
+    // is the total of the widths of the previous frames.
+    nsIFrame* inlineFrame = GetPrevContinuation(aFrame);
+    while (inlineFrame) {
+      if (!mPIStartBorderData.mFrame &&
+          !(mVertical ? inlineFrame->GetSkipSides().Top()
+                      : inlineFrame->GetSkipSides().Left())) {
+        mPIStartBorderData.mFrame = inlineFrame;
+      }
+      nsRect rect = inlineFrame->GetRect();
+      mContinuationPoint += mVertical ? rect.height : rect.width;
+      if (mBidiEnabled && !AreOnSameLine(aFrame, inlineFrame)) {
+        mLineContinuationPoint += mVertical ? rect.height : rect.width;
+      }
+      mUnbrokenMeasure += mVertical ? rect.height : rect.width;
+      mBoundingBox.UnionRect(mBoundingBox, rect);
+      inlineFrame = GetPrevContinuation(inlineFrame);
+    }
+
+    // Next add this frame and subsequent frames to the bounding box and
+    // unbroken width.
+    inlineFrame = aFrame;
+    while (inlineFrame) {
+      if (!mPIStartBorderData.mFrame &&
+          !(mVertical ? inlineFrame->GetSkipSides().Top()
+                      : inlineFrame->GetSkipSides().Left())) {
+        mPIStartBorderData.mFrame = inlineFrame;
+      }
+      nsRect rect = inlineFrame->GetRect();
+      mUnbrokenMeasure += mVertical ? rect.height : rect.width;
+      mBoundingBox.UnionRect(mBoundingBox, rect);
+      inlineFrame = GetNextContinuation(inlineFrame);
+    }
+
+    mFrame = aFrame;
+  }
+
+  bool AreOnSameLine(nsIFrame* aFrame1, nsIFrame* aFrame2) {
+    if (nsBlockFrame* blockFrame = do_QueryFrame(mLineContainer)) {
+      bool isValid1, isValid2;
+      nsBlockInFlowLineIterator it1(blockFrame, aFrame1, &isValid1);
+      nsBlockInFlowLineIterator it2(blockFrame, aFrame2, &isValid2);
+      return isValid1 && isValid2 &&
+        // Make sure aFrame1 and aFrame2 are in the same continuation of
+        // blockFrame.
+        it1.GetContainer() == it2.GetContainer() &&
+        // And on the same line in it
+        it1.GetLine() == it2.GetLine();
+    }
+    if (nsRubyTextContainerFrame* rtcFrame = do_QueryFrame(mLineContainer)) {
+      nsBlockFrame* block = nsLayoutUtils::FindNearestBlockAncestor(rtcFrame);
+      // Ruby text container can only hold one line of text, so if they
+      // are in the same continuation, they are in the same line. Since
+      // ruby text containers are bidi isolate, they are never split for
+      // bidi reordering, which means being in different continuation
+      // indicates being in different lines.
+      for (nsIFrame* frame = rtcFrame->FirstContinuation();
+           frame; frame = frame->GetNextContinuation()) {
+        bool isDescendant1 =
+          nsLayoutUtils::IsProperAncestorFrame(frame, aFrame1, block);
+        bool isDescendant2 =
+          nsLayoutUtils::IsProperAncestorFrame(frame, aFrame2, block);
+        if (isDescendant1 && isDescendant2) {
+          return true;
+        }
+        if (isDescendant1 || isDescendant2) {
+          return false;
+        }
+      }
+      MOZ_ASSERT_UNREACHABLE("None of the frames is a descendant of this rtc?");
+    }
+    MOZ_ASSERT_UNREACHABLE("Do we have any other type of line container?");
+    return false;
+  }
+};
+
+// A resolved color stop, with a specific position along the gradient line and
+// a color.
+struct ColorStop {
+  ColorStop(): mPosition(0), mIsMidpoint(false) {}
+  ColorStop(double aPosition, bool aIsMidPoint, const Color& aColor) :
+    mPosition(aPosition), mIsMidpoint(aIsMidPoint), mColor(aColor) {}
+  double mPosition; // along the gradient line; 0=start, 1=end
+  bool mIsMidpoint;
+  Color mColor;
+};
+
+/* Local functions */
+static DrawResult DrawBorderImage(nsPresContext* aPresContext,
+                                  nsRenderingContext& aRenderingContext,
+                                  nsIFrame* aForFrame,
+                                  const nsRect& aBorderArea,
+                                  const nsStyleBorder& aStyleBorder,
+                                  const nsRect& aDirtyRect,
+                                  Sides aSkipSides,
+                                  PaintBorderFlags aFlags);
+
+static nscolor MakeBevelColor(mozilla::css::Side whichSide, uint8_t style,
+                              nscolor aBackgroundColor,
+                              nscolor aBorderColor);
+
+static InlineBackgroundData* gInlineBGData = nullptr;
+
+// Initialize any static variables used by nsCSSRendering.
+void nsCSSRendering::Init()
+{
+  NS_ASSERTION(!gInlineBGData, "Init called twice");
+  gInlineBGData = new InlineBackgroundData();
+}
+
+// Clean up any global variables used by nsCSSRendering.
+void nsCSSRendering::Shutdown()
+{
+  delete gInlineBGData;
+  gInlineBGData = nullptr;
+}
+
+/**
+ * Make a bevel color
+ */
+static nscolor
+MakeBevelColor(mozilla::css::Side whichSide, uint8_t style,
+               nscolor aBackgroundColor, nscolor aBorderColor)
+{
+
+  nscolor colors[2];
+  nscolor theColor;
+
+  // Given a background color and a border color
+  // calculate the color used for the shading
+  NS_GetSpecial3DColors(colors, aBackgroundColor, aBorderColor);
+
+  if ((style == NS_STYLE_BORDER_STYLE_OUTSET) ||
+      (style == NS_STYLE_BORDER_STYLE_RIDGE)) {
+    // Flip colors for these two border styles
+    switch (whichSide) {
+    case NS_SIDE_BOTTOM: whichSide = NS_SIDE_TOP;    break;
+    case NS_SIDE_RIGHT:  whichSide = NS_SIDE_LEFT;   break;
+    case NS_SIDE_TOP:    whichSide = NS_SIDE_BOTTOM; break;
+    case NS_SIDE_LEFT:   whichSide = NS_SIDE_RIGHT;  break;
+    }
+  }
+
+  switch (whichSide) {
+  case NS_SIDE_BOTTOM:
+    theColor = colors[1];
+    break;
+  case NS_SIDE_RIGHT:
+    theColor = colors[1];
+    break;
+  case NS_SIDE_TOP:
+    theColor = colors[0];
+    break;
+  case NS_SIDE_LEFT:
+  default:
+    theColor = colors[0];
+    break;
+  }
+  return theColor;
+}
+
+static bool
+GetRadii(nsIFrame* aForFrame, const nsStyleBorder& aBorder,
+         const nsRect& aOrigBorderArea, const nsRect& aBorderArea,
+         nscoord aRadii[8])
+{
+  bool haveRoundedCorners;
+  nsSize sz = aBorderArea.Size();
+  nsSize frameSize = aForFrame->GetSize();
+  if (&aBorder == aForFrame->StyleBorder() &&
+      frameSize == aOrigBorderArea.Size()) {
+    haveRoundedCorners = aForFrame->GetBorderRadii(sz, sz, Sides(), aRadii);
+   } else {
+    haveRoundedCorners =
+      nsIFrame::ComputeBorderRadii(aBorder.mBorderRadius, frameSize, sz, Sides(), aRadii);
+  }
+
+  return haveRoundedCorners;
+}
+
+static bool
+GetRadii(nsIFrame* aForFrame, const nsStyleBorder& aBorder,
+         const nsRect& aOrigBorderArea, const nsRect& aBorderArea,
+         RectCornerRadii* aBgRadii)
+{
+  nscoord radii[8];
+  bool haveRoundedCorners = GetRadii(aForFrame, aBorder, aOrigBorderArea, aBorderArea, radii);
+
+  if (haveRoundedCorners) {
+    auto d2a = aForFrame->PresContext()->AppUnitsPerDevPixel();
+    nsCSSRendering::ComputePixelRadii(radii, d2a, aBgRadii);
+  }
+  return haveRoundedCorners;
+}
+
+static nsRect
+JoinBoxesForVerticalSlice(nsIFrame* aFrame, const nsRect& aBorderArea)
+{
+  // Inflate vertically as if our continuations were laid out vertically
+  // adjacent. Note that we don't touch the width.
+  nsRect borderArea = aBorderArea;
+  nscoord h = 0;
+  nsIFrame* f = aFrame->GetNextContinuation();
+  for (; f; f = f->GetNextContinuation()) {
+    MOZ_ASSERT(!(f->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT),
+               "anonymous ib-split block shouldn't have border/background");
+    h += f->GetRect().height;
+  }
+  borderArea.height += h;
+  h = 0;
+  f = aFrame->GetPrevContinuation();
+  for (; f; f = f->GetPrevContinuation()) {
+    MOZ_ASSERT(!(f->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT),
+               "anonymous ib-split block shouldn't have border/background");
+    h += f->GetRect().height;
+  }
+  borderArea.y -= h;
+  borderArea.height += h;
+  return borderArea;
+}
+
+/**
+ * Inflate aBorderArea which is relative to aFrame's origin to calculate
+ * a hypothetical non-split frame area for all the continuations.
+ * See "Joining Boxes for 'slice'" in
+ * http://dev.w3.org/csswg/css-break/#break-decoration
+ */
+enum InlineBoxOrder { eForBorder, eForBackground };
+static nsRect
+JoinBoxesForSlice(nsIFrame* aFrame, const nsRect& aBorderArea,
+                  InlineBoxOrder aOrder)
+{
+  if (static_cast<nsInlineFrame*>(do_QueryFrame(aFrame))) {
+    return (aOrder == eForBorder
+            ? gInlineBGData->GetBorderContinuousRect(aFrame, aBorderArea)
+            : gInlineBGData->GetContinuousRect(aFrame)) +
+      aBorderArea.TopLeft();
+  }
+  return JoinBoxesForVerticalSlice(aFrame, aBorderArea);
+}
+
+static bool
+IsBoxDecorationSlice(const nsStyleBorder& aStyleBorder)
+{
+  return aStyleBorder.mBoxDecorationBreak == StyleBoxDecorationBreak::Slice;
+}
+
+static nsRect
+BoxDecorationRectForBorder(nsIFrame* aFrame, const nsRect& aBorderArea,
+                           Sides aSkipSides,
+                           const nsStyleBorder* aStyleBorder = nullptr)
+{
+  if (!aStyleBorder) {
+    aStyleBorder = aFrame->StyleBorder();
+  }
+  // If aSkipSides.IsEmpty() then there are no continuations, or it's
+  // a ::first-letter that wants all border sides on the first continuation.
+  return ::IsBoxDecorationSlice(*aStyleBorder) && !aSkipSides.IsEmpty()
+           ? ::JoinBoxesForSlice(aFrame, aBorderArea, eForBorder)
+           : aBorderArea;
+}
+
+static nsRect
+BoxDecorationRectForBackground(nsIFrame* aFrame, const nsRect& aBorderArea,
+                               Sides aSkipSides,
+                               const nsStyleBorder* aStyleBorder = nullptr)
+{
+  if (!aStyleBorder) {
+    aStyleBorder = aFrame->StyleBorder();
+  }
+  // If aSkipSides.IsEmpty() then there are no continuations, or it's
+  // a ::first-letter that wants all border sides on the first continuation.
+  return ::IsBoxDecorationSlice(*aStyleBorder) && !aSkipSides.IsEmpty()
+           ? ::JoinBoxesForSlice(aFrame, aBorderArea, eForBackground)
+           : aBorderArea;
+}
+
+//----------------------------------------------------------------------
+// Thebes Border Rendering Code Start
+
+/*
+ * Compute the float-pixel radii that should be used for drawing
+ * this border/outline, given the various input bits.
+ */
+/* static */ void
+nsCSSRendering::ComputePixelRadii(const nscoord *aAppUnitsRadii,
+                                  nscoord aAppUnitsPerPixel,
+                                  RectCornerRadii *oBorderRadii)
+{
+  Float radii[8];
+  NS_FOR_CSS_HALF_CORNERS(corner)
+    radii[corner] = Float(aAppUnitsRadii[corner]) / aAppUnitsPerPixel;
+
+  (*oBorderRadii)[C_TL] = Size(radii[NS_CORNER_TOP_LEFT_X],
+                               radii[NS_CORNER_TOP_LEFT_Y]);
+  (*oBorderRadii)[C_TR] = Size(radii[NS_CORNER_TOP_RIGHT_X],
+                               radii[NS_CORNER_TOP_RIGHT_Y]);
+  (*oBorderRadii)[C_BR] = Size(radii[NS_CORNER_BOTTOM_RIGHT_X],
+                               radii[NS_CORNER_BOTTOM_RIGHT_Y]);
+  (*oBorderRadii)[C_BL] = Size(radii[NS_CORNER_BOTTOM_LEFT_X],
+                               radii[NS_CORNER_BOTTOM_LEFT_Y]);
+}
+
+DrawResult
+nsCSSRendering::PaintBorder(nsPresContext* aPresContext,
+                            nsRenderingContext& aRenderingContext,
+                            nsIFrame* aForFrame,
+                            const nsRect& aDirtyRect,
+                            const nsRect& aBorderArea,
+                            nsStyleContext* aStyleContext,
+                            PaintBorderFlags aFlags,
+                            Sides aSkipSides)
+{
+  PROFILER_LABEL("nsCSSRendering", "PaintBorder",
+    js::ProfileEntry::Category::GRAPHICS);
+
+  nsStyleContext *styleIfVisited = aStyleContext->GetStyleIfVisited();
+  const nsStyleBorder *styleBorder = aStyleContext->StyleBorder();
+  // Don't check RelevantLinkVisited here, since we want to take the
+  // same amount of time whether or not it's true.
+  if (!styleIfVisited) {
+    return PaintBorderWithStyleBorder(aPresContext, aRenderingContext, aForFrame,
+                                      aDirtyRect, aBorderArea, *styleBorder,
+                                      aStyleContext, aFlags, aSkipSides);
+  }
+
+  nsStyleBorder newStyleBorder(*styleBorder);
+
+  NS_FOR_CSS_SIDES(side) {
+    nscolor color = aStyleContext->GetVisitedDependentColor(
+      nsCSSProps::SubpropertyEntryFor(eCSSProperty_border_color)[side]);
+    newStyleBorder.mBorderColor[side] = StyleComplexColor::FromColor(color);
+  }
+  DrawResult result =
+    PaintBorderWithStyleBorder(aPresContext, aRenderingContext, aForFrame,
+                               aDirtyRect, aBorderArea, newStyleBorder,
+                               aStyleContext, aFlags, aSkipSides);
+
+  return result;
+}
+
+DrawResult
+nsCSSRendering::PaintBorderWithStyleBorder(nsPresContext* aPresContext,
+                                           nsRenderingContext& aRenderingContext,
+                                           nsIFrame* aForFrame,
+                                           const nsRect& aDirtyRect,
+                                           const nsRect& aBorderArea,
+                                           const nsStyleBorder& aStyleBorder,
+                                           nsStyleContext* aStyleContext,
+                                           PaintBorderFlags aFlags,
+                                           Sides aSkipSides)
+{
+  DrawTarget& aDrawTarget = *aRenderingContext.GetDrawTarget();
+
+  PrintAsStringNewline("++ PaintBorder");
+
+  // Check to see if we have an appearance defined.  If so, we let the theme
+  // renderer draw the border.  DO not get the data from aForFrame, since the passed in style context
+  // may be different!  Always use |aStyleContext|!
+  const nsStyleDisplay* displayData = aStyleContext->StyleDisplay();
+  if (displayData->mAppearance) {
+    nsITheme *theme = aPresContext->GetTheme();
+    if (theme &&
+        theme->ThemeSupportsWidget(aPresContext, aForFrame,
+                                   displayData->mAppearance)) {
+      return DrawResult::SUCCESS; // Let the theme handle it.
+    }
+  }
+
+  if (aStyleBorder.IsBorderImageLoaded()) {
+    return DrawBorderImage(aPresContext, aRenderingContext, aForFrame,
+                           aBorderArea, aStyleBorder, aDirtyRect,
+                           aSkipSides, aFlags);
+  }
+
+  DrawResult result = DrawResult::SUCCESS;
+
+  // If we had a border-image, but it wasn't loaded, then we should return
+  // DrawResult::NOT_READY; we'll want to try again if we do a paint with sync
+  // decoding enabled.
+  if (aStyleBorder.mBorderImageSource.GetType() != eStyleImageType_Null) {
+    result = DrawResult::NOT_READY;
+  }
+
+  // Get our style context's color struct.
+  const nsStyleColor* ourColor = aStyleContext->StyleColor();
+
+  // In NavQuirks mode we want to use the parent's context as a starting point
+  // for determining the background color.
+  bool quirks = aPresContext->CompatibilityMode() == eCompatibility_NavQuirks;
+  nsIFrame* bgFrame = FindNonTransparentBackgroundFrame(aForFrame, quirks);
+  nsStyleContext* bgContext = bgFrame->StyleContext();
+  nscolor bgColor =
+    bgContext->GetVisitedDependentColor(eCSSProperty_background_color);
+
+  nsMargin border = aStyleBorder.GetComputedBorder();
+  if (0 == border.left && 0 == border.right &&
+      0 == border.top  && 0 == border.bottom) {
+    // Empty border area
+    return result;
+  }
+
+  // Compute the outermost boundary of the area that might be painted.
+  // Same coordinate space as aBorderArea & aBGClipRect.
+  nsRect joinedBorderArea =
+    ::BoxDecorationRectForBorder(aForFrame, aBorderArea, aSkipSides, &aStyleBorder);
+  RectCornerRadii bgRadii;
+  ::GetRadii(aForFrame, aStyleBorder, aBorderArea, joinedBorderArea, &bgRadii);
+
+  PrintAsFormatString(" joinedBorderArea: %d %d %d %d\n", joinedBorderArea.x, joinedBorderArea.y,
+     joinedBorderArea.width, joinedBorderArea.height);
+
+  // start drawing
+  bool needToPopClip = false;
+
+  if (::IsBoxDecorationSlice(aStyleBorder)) {
+    if (joinedBorderArea.IsEqualEdges(aBorderArea)) {
+      // No need for a clip, just skip the sides we don't want.
+      border.ApplySkipSides(aSkipSides);
+    } else {
+      // We're drawing borders around the joined continuation boxes so we need
+      // to clip that to the slice that we want for this frame.
+      aDrawTarget.PushClipRect(
+        NSRectToSnappedRect(aBorderArea,
+                            aForFrame->PresContext()->AppUnitsPerDevPixel(),
+                            aDrawTarget));
+      needToPopClip = true;
+    }
+  } else {
+    MOZ_ASSERT(joinedBorderArea.IsEqualEdges(aBorderArea),
+               "Should use aBorderArea for box-decoration-break:clone");
+    MOZ_ASSERT(aForFrame->GetSkipSides().IsEmpty() ||
+               IS_TRUE_OVERFLOW_CONTAINER(aForFrame),
+               "Should not skip sides for box-decoration-break:clone except "
+               "::first-letter/line continuations or other frame types that "
+               "don't have borders but those shouldn't reach this point. "
+               "Overflow containers do reach this point though.");
+    border.ApplySkipSides(aSkipSides);
+  }
+
+  // Convert to dev pixels.
+  nscoord twipsPerPixel = aPresContext->DevPixelsToAppUnits(1);
+  Rect joinedBorderAreaPx = NSRectToRect(joinedBorderArea, twipsPerPixel);
+  Float borderWidths[4] = { Float(border.top / twipsPerPixel),
+                            Float(border.right / twipsPerPixel),
+                            Float(border.bottom / twipsPerPixel),
+                            Float(border.left / twipsPerPixel) };
+  Rect dirtyRect = NSRectToRect(aDirtyRect, twipsPerPixel);
+
+  uint8_t borderStyles[4];
+  nscolor borderColors[4];
+  nsBorderColors *compositeColors[4];
+
+  // pull out styles, colors, composite colors
+  NS_FOR_CSS_SIDES (i) {
+    borderStyles[i] = aStyleBorder.GetBorderStyle(i);
+    borderColors[i] = ourColor->CalcComplexColor(aStyleBorder.mBorderColor[i]);
+    aStyleBorder.GetCompositeColors(i, &compositeColors[i]);
+  }
+
+  PrintAsFormatString(" borderStyles: %d %d %d %d\n", borderStyles[0], borderStyles[1], borderStyles[2], borderStyles[3]);
+  //PrintAsFormatString ("bgRadii: %f %f %f %f\n", bgRadii[0], bgRadii[1], bgRadii[2], bgRadii[3]);
+
+#if 0
+  // this will draw a transparent red backround underneath the border area
+  ColorPattern color(ToDeviceColor(Color(1.f, 0.f, 0.f, 0.5f)));
+  aDrawTarget.FillRect(joinedBorderAreaPx, color);
+#endif
+
+  nsIDocument* document = nullptr;
+  nsIContent* content = aForFrame->GetContent();
+  if (content) {
+    document = content->OwnerDoc();
+  }
+
+  nsCSSBorderRenderer br(aPresContext,
+                         document,
+                         &aDrawTarget,
+                         dirtyRect,
+                         joinedBorderAreaPx,
+                         borderStyles,
+                         borderWidths,
+                         bgRadii,
+                         borderColors,
+                         compositeColors,
+                         bgColor);
+  br.DrawBorders();
+
+  if (needToPopClip) {
+    aDrawTarget.PopClip();
+  }
+
+  PrintAsStringNewline();
+
+  return result;
+}
+
+static nsRect
+GetOutlineInnerRect(nsIFrame* aFrame)
+{
+  nsRect* savedOutlineInnerRect =
+    aFrame->Properties().Get(nsIFrame::OutlineInnerRectProperty());
+  if (savedOutlineInnerRect)
+    return *savedOutlineInnerRect;
+  NS_NOTREACHED("we should have saved a frame property");
+  return nsRect(nsPoint(0, 0), aFrame->GetSize());
+}
+
+void
+nsCSSRendering::PaintOutline(nsPresContext* aPresContext,
+                             nsRenderingContext& aRenderingContext,
+                             nsIFrame* aForFrame,
+                             const nsRect& aDirtyRect,
+                             const nsRect& aBorderArea,
+                             nsStyleContext* aStyleContext)
+{
+  nscoord             twipsRadii[8];
+
+  // Get our style context's color struct.
+  const nsStyleOutline* ourOutline = aStyleContext->StyleOutline();
+  MOZ_ASSERT(ourOutline != NS_STYLE_BORDER_STYLE_NONE,
+             "shouldn't have created nsDisplayOutline item");
+
+  uint8_t outlineStyle = ourOutline->mOutlineStyle;
+  nscoord width = ourOutline->GetOutlineWidth();
+
+  if (width == 0 && outlineStyle != NS_STYLE_BORDER_STYLE_AUTO) {
+    // Empty outline
+    return;
+  }
+
+  nsIFrame* bgFrame = nsCSSRendering::FindNonTransparentBackgroundFrame
+    (aForFrame, false);
+  nsStyleContext* bgContext = bgFrame->StyleContext();
+  nscolor bgColor =
+    bgContext->GetVisitedDependentColor(eCSSProperty_background_color);
+
+  nsRect innerRect;
+  if (
+#ifdef MOZ_XUL
+      aStyleContext->GetPseudoType() == CSSPseudoElementType::XULTree
+#else
+      false
+#endif
+     ) {
+    innerRect = aBorderArea;
+  } else {
+    innerRect = GetOutlineInnerRect(aForFrame) + aBorderArea.TopLeft();
+  }
+  nscoord offset = ourOutline->mOutlineOffset;
+  innerRect.Inflate(offset, offset);
+  // If the dirty rect is completely inside the border area (e.g., only the
+  // content is being painted), then we can skip out now
+  // XXX this isn't exactly true for rounded borders, where the inside curves may
+  // encroach into the content area.  A safer calculation would be to
+  // shorten insideRect by the radius one each side before performing this test.
+  if (innerRect.Contains(aDirtyRect))
+    return;
+
+  nsRect outerRect = innerRect;
+  outerRect.Inflate(width, width);
+
+  // get the radius for our outline
+  nsIFrame::ComputeBorderRadii(ourOutline->mOutlineRadius, aBorderArea.Size(),
+                               outerRect.Size(), Sides(), twipsRadii);
+
+  // Get our conversion values
+  nscoord twipsPerPixel = aPresContext->DevPixelsToAppUnits(1);
+
+  // get the outer rectangles
+  Rect oRect(NSRectToRect(outerRect, twipsPerPixel));
+
+  // convert the radii
+  nsMargin outlineMargin(width, width, width, width);
+  RectCornerRadii outlineRadii;
+  ComputePixelRadii(twipsRadii, twipsPerPixel, &outlineRadii);
+
+  if (outlineStyle == NS_STYLE_BORDER_STYLE_AUTO) {
+    if (nsLayoutUtils::IsOutlineStyleAutoEnabled()) {
+      nsITheme* theme = aPresContext->GetTheme();
+      if (theme && theme->ThemeSupportsWidget(aPresContext, aForFrame,
+                                              NS_THEME_FOCUS_OUTLINE)) {
+        theme->DrawWidgetBackground(&aRenderingContext, aForFrame,
+                                    NS_THEME_FOCUS_OUTLINE, innerRect,
+                                    aDirtyRect);
+        return;
+      }
+    }
+    if (width == 0) {
+      return; // empty outline
+    }
+    // http://dev.w3.org/csswg/css-ui/#outline
+    // "User agents may treat 'auto' as 'solid'."
+    outlineStyle = NS_STYLE_BORDER_STYLE_SOLID;
+  }
+
+  uint8_t outlineStyles[4] = { outlineStyle, outlineStyle,
+                               outlineStyle, outlineStyle };
+
+  // This handles treating the initial color as 'currentColor'; if we
+  // ever want 'invert' back we'll need to do a bit of work here too.
+  nscolor outlineColor =
+    aStyleContext->GetVisitedDependentColor(eCSSProperty_outline_color);
+  nscolor outlineColors[4] = { outlineColor,
+                               outlineColor,
+                               outlineColor,
+                               outlineColor };
+
+  // convert the border widths
+  Float outlineWidths[4] = { Float(width / twipsPerPixel),
+                             Float(width / twipsPerPixel),
+                             Float(width / twipsPerPixel),
+                             Float(width / twipsPerPixel) };
+  Rect dirtyRect = NSRectToRect(aDirtyRect, twipsPerPixel);
+
+  nsIDocument* document = nullptr;
+  nsIContent* content = aForFrame->GetContent();
+  if (content) {
+    document = content->OwnerDoc();
+  }
+
+  // start drawing
+
+  nsCSSBorderRenderer br(aPresContext,
+                         document,
+                         aRenderingContext.GetDrawTarget(),
+                         dirtyRect,
+                         oRect,
+                         outlineStyles,
+                         outlineWidths,
+                         outlineRadii,
+                         outlineColors,
+                         nullptr,
+                         bgColor);
+  br.DrawBorders();
+
+  PrintAsStringNewline();
+}
+
+void
+nsCSSRendering::PaintFocus(nsPresContext* aPresContext,
+                           DrawTarget* aDrawTarget,
+                           const nsRect& aFocusRect,
+                           nscolor aColor)
+{
+  nscoord oneCSSPixel = nsPresContext::CSSPixelsToAppUnits(1);
+  nscoord oneDevPixel = aPresContext->DevPixelsToAppUnits(1);
+
+  Rect focusRect(NSRectToRect(aFocusRect, oneDevPixel));
+
+  RectCornerRadii focusRadii;
+  {
+    nscoord twipsRadii[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
+    ComputePixelRadii(twipsRadii, oneDevPixel, &focusRadii);
+  }
+  Float focusWidths[4] = { Float(oneCSSPixel / oneDevPixel),
+                           Float(oneCSSPixel / oneDevPixel),
+                           Float(oneCSSPixel / oneDevPixel),
+                           Float(oneCSSPixel / oneDevPixel) };
+
+  uint8_t focusStyles[4] = { NS_STYLE_BORDER_STYLE_DOTTED,
+                             NS_STYLE_BORDER_STYLE_DOTTED,
+                             NS_STYLE_BORDER_STYLE_DOTTED,
+                             NS_STYLE_BORDER_STYLE_DOTTED };
+  nscolor focusColors[4] = { aColor, aColor, aColor, aColor };
+
+  // Because this renders a dotted border, the background color
+  // should not be used.  Therefore, we provide a value that will
+  // be blatantly wrong if it ever does get used.  (If this becomes
+  // something that CSS can style, this function will then have access
+  // to a style context and can use the same logic that PaintBorder
+  // and PaintOutline do.)
+  nsCSSBorderRenderer br(aPresContext,
+                         nullptr,
+                         aDrawTarget,
+                         focusRect,
+                         focusRect,
+                         focusStyles,
+                         focusWidths,
+                         focusRadii,
+                         focusColors,
+                         nullptr,
+                         NS_RGB(255, 0, 0));
+  br.DrawBorders();
+
+  PrintAsStringNewline();
+}
+
+// Thebes Border Rendering Code End
+//----------------------------------------------------------------------
+
+
+//----------------------------------------------------------------------
+
+/**
+ * Helper for ComputeObjectAnchorPoint; parameters are the same as for
+ * that function, except they're for a single coordinate / a single size
+ * dimension. (so, x/width vs. y/height)
+ */
+static void
+ComputeObjectAnchorCoord(const Position::Coord& aCoord,
+                         const nscoord aOriginBounds,
+                         const nscoord aImageSize,
+                         nscoord* aTopLeftCoord,
+                         nscoord* aAnchorPointCoord)
+{
+  *aAnchorPointCoord = aCoord.mLength;
+  *aTopLeftCoord = aCoord.mLength;
+
+  if (aCoord.mHasPercent) {
+    // Adjust aTopLeftCoord by the specified % of the extra space.
+    nscoord extraSpace = aOriginBounds - aImageSize;
+    *aTopLeftCoord += NSToCoordRound(aCoord.mPercent * extraSpace);
+
+    // The anchor-point doesn't care about our image's size; just the size
+    // of the region we're rendering into.
+    *aAnchorPointCoord += NSToCoordRound(aCoord.mPercent * aOriginBounds);
+  }
+}
+
+void
+nsImageRenderer::ComputeObjectAnchorPoint(
+  const Position& aPos,
+  const nsSize& aOriginBounds,
+  const nsSize& aImageSize,
+  nsPoint* aTopLeft,
+  nsPoint* aAnchorPoint)
+{
+  ComputeObjectAnchorCoord(aPos.mXPosition,
+                           aOriginBounds.width, aImageSize.width,
+                           &aTopLeft->x, &aAnchorPoint->x);
+
+  ComputeObjectAnchorCoord(aPos.mYPosition,
+                           aOriginBounds.height, aImageSize.height,
+                           &aTopLeft->y, &aAnchorPoint->y);
+}
+
+nsIFrame*
+nsCSSRendering::FindNonTransparentBackgroundFrame(nsIFrame* aFrame,
+                                                  bool aStartAtParent /*= false*/)
+{
+  NS_ASSERTION(aFrame, "Cannot find NonTransparentBackgroundFrame in a null frame");
+
+  nsIFrame* frame = nullptr;
+  if (aStartAtParent) {
+    frame = nsLayoutUtils::GetParentOrPlaceholderFor(aFrame);
+  }
+  if (!frame) {
+    frame = aFrame;
+  }
+
+  while (frame) {
+    // No need to call GetVisitedDependentColor because it always uses
+    // this alpha component anyway.
+    if (NS_GET_A(frame->StyleBackground()->mBackgroundColor) > 0)
+      break;
+
+    if (frame->IsThemed())
+      break;
+
+    nsIFrame* parent = nsLayoutUtils::GetParentOrPlaceholderFor(frame);
+    if (!parent)
+      break;
+
+    frame = parent;
+  }
+  return frame;
+}
+
+// Returns true if aFrame is a canvas frame.
+// We need to treat the viewport as canvas because, even though
+// it does not actually paint a background, we need to get the right
+// background style so we correctly detect transparent documents.
+bool
+nsCSSRendering::IsCanvasFrame(nsIFrame* aFrame)
+{
+  nsIAtom* frameType = aFrame->GetType();
+  return frameType == nsGkAtoms::canvasFrame ||
+         frameType == nsGkAtoms::rootFrame ||
+         frameType == nsGkAtoms::pageContentFrame ||
+         frameType == nsGkAtoms::viewportFrame;
+}
+
+nsIFrame*
+nsCSSRendering::FindBackgroundStyleFrame(nsIFrame* aForFrame)
+{
+  const nsStyleBackground* result = aForFrame->StyleBackground();
+
+  // Check if we need to do propagation from BODY rather than HTML.
+  if (!result->IsTransparent()) {
+    return aForFrame;
+  }
+
+  nsIContent* content = aForFrame->GetContent();
+  // The root element content can't be null. We wouldn't know what
+  // frame to create for aFrame.
+  // Use |OwnerDoc| so it works during destruction.
+  if (!content) {
+    return aForFrame;
+  }
+
+  nsIDocument* document = content->OwnerDoc();
+
+  dom::Element* bodyContent = document->GetBodyElement();
+  // We need to null check the body node (bug 118829) since
+  // there are cases, thanks to the fix for bug 5569, where we
+  // will reflow a document with no body.  In particular, if a
+  // SCRIPT element in the head blocks the parser and then has a
+  // SCRIPT that does "document.location.href = 'foo'", then
+  // nsParser::Terminate will call |DidBuildModel| methods
+  // through to the content sink, which will call |StartLayout|
+  // and thus |Initialize| on the pres shell.  See bug 119351
+  // for the ugly details.
+  if (!bodyContent) {
+    return aForFrame;
+  }
+
+  nsIFrame *bodyFrame = bodyContent->GetPrimaryFrame();
+  if (!bodyFrame) {
+    return aForFrame;
+  }
+
+  return nsLayoutUtils::GetStyleFrame(bodyFrame);
+}
+
+/**
+ * |FindBackground| finds the correct style data to use to paint the
+ * background.  It is responsible for handling the following two
+ * statements in section 14.2 of CSS2:
+ *
+ *   The background of the box generated by the root element covers the
+ *   entire canvas.
+ *
+ *   For HTML documents, however, we recommend that authors specify the
+ *   background for the BODY element rather than the HTML element. User
+ *   agents should observe the following precedence rules to fill in the
+ *   background: if the value of the 'background' property for the HTML
+ *   element is different from 'transparent' then use it, else use the
+ *   value of the 'background' property for the BODY element. If the
+ *   resulting value is 'transparent', the rendering is undefined.
+ *
+ * Thus, in our implementation, it is responsible for ensuring that:
+ *  + we paint the correct background on the |nsCanvasFrame|,
+ *    |nsRootBoxFrame|, or |nsPageFrame|,
+ *  + we don't paint the background on the root element, and
+ *  + we don't paint the background on the BODY element in *some* cases,
+ *    and for SGML-based HTML documents only.
+ *
+ * |FindBackground| returns true if a background should be painted, and
+ * the resulting style context to use for the background information
+ * will be filled in to |aBackground|.
+ */
+nsStyleContext*
+nsCSSRendering::FindRootFrameBackground(nsIFrame* aForFrame)
+{
+  return FindBackgroundStyleFrame(aForFrame)->StyleContext();
+}
+
+inline bool
+FindElementBackground(nsIFrame* aForFrame, nsIFrame* aRootElementFrame,
+                      nsStyleContext** aBackgroundSC)
+{
+  if (aForFrame == aRootElementFrame) {
+    // We must have propagated our background to the viewport or canvas. Abort.
+    return false;
+  }
+
+  *aBackgroundSC = aForFrame->StyleContext();
+
+  // Return true unless the frame is for a BODY element whose background
+  // was propagated to the viewport.
+
+  nsIContent* content = aForFrame->GetContent();
+  if (!content || content->NodeInfo()->NameAtom() != nsGkAtoms::body)
+    return true; // not frame for a "body" element
+  // It could be a non-HTML "body" element but that's OK, we'd fail the
+  // bodyContent check below
+
+  if (aForFrame->StyleContext()->GetPseudo())
+    return true; // A pseudo-element frame.
+
+  // We should only look at the <html> background if we're in an HTML document
+  nsIDocument* document = content->OwnerDoc();
+
+  dom::Element* bodyContent = document->GetBodyElement();
+  if (bodyContent != content)
+    return true; // this wasn't the background that was propagated
+
+  // This can be called even when there's no root element yet, during frame
+  // construction, via nsLayoutUtils::FrameHasTransparency and
+  // nsContainerFrame::SyncFrameViewProperties.
+  if (!aRootElementFrame)
+    return true;
+
+  const nsStyleBackground* htmlBG = aRootElementFrame->StyleBackground();
+  return !htmlBG->IsTransparent();
+}
+
+bool
+nsCSSRendering::FindBackground(nsIFrame* aForFrame,
+                               nsStyleContext** aBackgroundSC)
+{
+  nsIFrame* rootElementFrame =
+    aForFrame->PresContext()->PresShell()->FrameConstructor()->GetRootElementStyleFrame();
+  if (IsCanvasFrame(aForFrame)) {
+    *aBackgroundSC = FindCanvasBackground(aForFrame, rootElementFrame);
+    return true;
+  } else {
+    return FindElementBackground(aForFrame, rootElementFrame, aBackgroundSC);
+  }
+}
+
+void
+nsCSSRendering::BeginFrameTreesLocked()
+{
+  ++gFrameTreeLockCount;
+}
+
+void
+nsCSSRendering::EndFrameTreesLocked()
+{
+  NS_ASSERTION(gFrameTreeLockCount > 0, "Unbalanced EndFrameTreeLocked");
+  --gFrameTreeLockCount;
+  if (gFrameTreeLockCount == 0) {
+    gInlineBGData->Reset();
+  }
+}
+
+void
+nsCSSRendering::PaintBoxShadowOuter(nsPresContext* aPresContext,
+                                    nsRenderingContext& aRenderingContext,
+                                    nsIFrame* aForFrame,
+                                    const nsRect& aFrameArea,
+                                    const nsRect& aDirtyRect,
+                                    float aOpacity)
+{
+  DrawTarget& aDrawTarget = *aRenderingContext.GetDrawTarget();
+  nsCSSShadowArray* shadows = aForFrame->StyleEffects()->mBoxShadow;
+  if (!shadows)
+    return;
+
+  bool hasBorderRadius;
+  bool nativeTheme; // mutually exclusive with hasBorderRadius
+  const nsStyleDisplay* styleDisplay = aForFrame->StyleDisplay();
+  nsITheme::Transparency transparency;
+  if (aForFrame->IsThemed(styleDisplay, &transparency)) {
+    // We don't respect border-radius for native-themed widgets
+    hasBorderRadius = false;
+    // For opaque (rectangular) theme widgets we can take the generic
+    // border-box path with border-radius disabled.
+    nativeTheme = transparency != nsITheme::eOpaque;
+  } else {
+    nativeTheme = false;
+    hasBorderRadius = true; // we'll update this below
+  }
+
+  nsRect frameRect = nativeTheme ?
+    aForFrame->GetVisualOverflowRectRelativeToSelf() + aFrameArea.TopLeft() :
+    aFrameArea;
+  Sides skipSides = aForFrame->GetSkipSides();
+  frameRect = ::BoxDecorationRectForBorder(aForFrame, frameRect, skipSides);
+
+  // Get any border radius, since box-shadow must also have rounded corners if
+  // the frame does.
+  RectCornerRadii borderRadii;
+  const nscoord twipsPerPixel = aPresContext->DevPixelsToAppUnits(1);
+  if (hasBorderRadius) {
+    nscoord twipsRadii[8];
+    NS_ASSERTION(aFrameArea.Size() == aForFrame->VisualBorderRectRelativeToSelf().Size(),
+                 "unexpected size");
+    nsSize sz = frameRect.Size();
+    hasBorderRadius = aForFrame->GetBorderRadii(sz, sz, Sides(), twipsRadii);
+    if (hasBorderRadius) {
+      ComputePixelRadii(twipsRadii, twipsPerPixel, &borderRadii);
+    }
+  }
+
+
+  // We don't show anything that intersects with the frame we're blurring on. So tell the
+  // blurrer not to do unnecessary work there.
+  gfxRect skipGfxRect = ThebesRect(NSRectToRect(frameRect, twipsPerPixel));
+  skipGfxRect.Round();
+  bool useSkipGfxRect = true;
+  if (nativeTheme) {
+    // Optimize non-leaf native-themed frames by skipping computing pixels
+    // in the padding-box. We assume the padding-box is going to be painted
+    // opaquely for non-leaf frames.
+    // XXX this may not be a safe assumption; we should make this go away
+    // by optimizing box-shadow drawing more for the cases where we don't have a skip-rect.
+    useSkipGfxRect = !aForFrame->IsLeaf();
+    nsRect paddingRect =
+      aForFrame->GetPaddingRect() - aForFrame->GetPosition() + aFrameArea.TopLeft();
+    skipGfxRect = nsLayoutUtils::RectToGfxRect(paddingRect, twipsPerPixel);
+  } else if (hasBorderRadius) {
+    skipGfxRect.Deflate(gfxMargin(
+        std::max(borderRadii[C_TL].height, borderRadii[C_TR].height), 0,
+        std::max(borderRadii[C_BL].height, borderRadii[C_BR].height), 0));
+  }
+
+  gfxContext* renderContext = aRenderingContext.ThebesContext();
+
+  for (uint32_t i = shadows->Length(); i > 0; --i) {
+    nsCSSShadowItem* shadowItem = shadows->ShadowAt(i - 1);
+    if (shadowItem->mInset)
+      continue;
+
+    nsRect shadowRect = frameRect;
+    shadowRect.MoveBy(shadowItem->mXOffset, shadowItem->mYOffset);
+    if (!nativeTheme) {
+      shadowRect.Inflate(shadowItem->mSpread, shadowItem->mSpread);
+    }
+
+    // shadowRect won't include the blur, so make an extra rect here that includes the blur
+    // for use in the even-odd rule below.
+    nsRect shadowRectPlusBlur = shadowRect;
+    nscoord blurRadius = shadowItem->mRadius;
+    shadowRectPlusBlur.Inflate(
+      nsContextBoxBlur::GetBlurRadiusMargin(blurRadius, twipsPerPixel));
+
+    Rect shadowGfxRectPlusBlur =
+      NSRectToRect(shadowRectPlusBlur, twipsPerPixel);
+    shadowGfxRectPlusBlur.RoundOut();
+    MaybeSnapToDevicePixels(shadowGfxRectPlusBlur, aDrawTarget, true);
+
+    // Set the shadow color; if not specified, use the foreground color
+    nscolor shadowColor;
+    if (shadowItem->mHasColor)
+      shadowColor = shadowItem->mColor;
+    else
+      shadowColor = aForFrame->StyleColor()->mColor;
+
+    Color gfxShadowColor(Color::FromABGR(shadowColor));
+    gfxShadowColor.a *= aOpacity;
+
+    if (nativeTheme) {
+      nsContextBoxBlur blurringArea;
+
+      // When getting the widget shape from the native theme, we're going
+      // to draw the widget into the shadow surface to create a mask.
+      // We need to ensure that there actually *is* a shadow surface
+      // and that we're not going to draw directly into renderContext.
+      gfxContext* shadowContext =
+        blurringArea.Init(shadowRect, shadowItem->mSpread,
+                          blurRadius, twipsPerPixel, renderContext, aDirtyRect,
+                          useSkipGfxRect ? &skipGfxRect : nullptr,
+                          nsContextBoxBlur::FORCE_MASK);
+      if (!shadowContext)
+        continue;
+
+      MOZ_ASSERT(shadowContext == blurringArea.GetContext());
+
+      renderContext->Save();
+      renderContext->SetColor(gfxShadowColor);
+
+      // Draw the shape of the frame so it can be blurred. Recall how nsContextBoxBlur
+      // doesn't make any temporary surfaces if blur is 0 and it just returns the original
+      // surface? If we have no blur, we're painting this fill on the actual content surface
+      // (renderContext == shadowContext) which is why we set up the color and clip
+      // before doing this.
+
+      // We don't clip the border-box from the shadow, nor any other box.
+      // We assume that the native theme is going to paint over the shadow.
+
+      // Draw the widget shape
+      gfxContextMatrixAutoSaveRestore save(shadowContext);
+      gfxPoint devPixelOffset =
+        nsLayoutUtils::PointToGfxPoint(nsPoint(shadowItem->mXOffset,
+                                               shadowItem->mYOffset),
+                                       aPresContext->AppUnitsPerDevPixel());
+      shadowContext->SetMatrix(
+        shadowContext->CurrentMatrix().Translate(devPixelOffset));
+
+      nsRect nativeRect = aDirtyRect;
+      nativeRect.MoveBy(-nsPoint(shadowItem->mXOffset, shadowItem->mYOffset));
+      nativeRect.IntersectRect(frameRect, nativeRect);
+      nsRenderingContext wrapperCtx(shadowContext);
+      aPresContext->GetTheme()->DrawWidgetBackground(&wrapperCtx, aForFrame,
+          styleDisplay->mAppearance, aFrameArea, nativeRect);
+
+      blurringArea.DoPaint();
+      renderContext->Restore();
+    } else {
+      renderContext->Save();
+
+      {
+        Rect innerClipRect = NSRectToRect(frameRect, twipsPerPixel);
+        if (!MaybeSnapToDevicePixels(innerClipRect, aDrawTarget, true)) {
+          innerClipRect.Round();
+        }
+
+        // Clip out the interior of the frame's border edge so that the shadow
+        // is only painted outside that area.
+        RefPtr<PathBuilder> builder =
+          aDrawTarget.CreatePathBuilder(FillRule::FILL_EVEN_ODD);
+        AppendRectToPath(builder, shadowGfxRectPlusBlur);
+        if (hasBorderRadius) {
+          AppendRoundedRectToPath(builder, innerClipRect, borderRadii);
+        } else {
+          AppendRectToPath(builder, innerClipRect);
+        }
+        RefPtr<Path> path = builder->Finish();
+        renderContext->Clip(path);
+      }
+
+      // Clip the shadow so that we only get the part that applies to aForFrame.
+      nsRect fragmentClip = shadowRectPlusBlur;
+      if (!skipSides.IsEmpty()) {
+        if (skipSides.Left()) {
+          nscoord xmost = fragmentClip.XMost();
+          fragmentClip.x = aFrameArea.x;
+          fragmentClip.width = xmost - fragmentClip.x;
+        }
+        if (skipSides.Right()) {
+          nscoord xmost = fragmentClip.XMost();
+          nscoord overflow = xmost - aFrameArea.XMost();
+          if (overflow > 0) {
+            fragmentClip.width -= overflow;
+          }
+        }
+        if (skipSides.Top()) {
+          nscoord ymost = fragmentClip.YMost();
+          fragmentClip.y = aFrameArea.y;
+          fragmentClip.height = ymost - fragmentClip.y;
+        }
+        if (skipSides.Bottom()) {
+          nscoord ymost = fragmentClip.YMost();
+          nscoord overflow = ymost - aFrameArea.YMost();
+          if (overflow > 0) {
+            fragmentClip.height -= overflow;
+          }
+        }
+      }
+      fragmentClip = fragmentClip.Intersect(aDirtyRect);
+      renderContext->
+        Clip(NSRectToSnappedRect(fragmentClip,
+                                 aForFrame->PresContext()->AppUnitsPerDevPixel(),
+                                 aDrawTarget));
+
+      RectCornerRadii clipRectRadii;
+      if (hasBorderRadius) {
+        Float spreadDistance = shadowItem->mSpread / twipsPerPixel;
+
+        Float borderSizes[4];
+
+        borderSizes[NS_SIDE_LEFT] = spreadDistance;
+        borderSizes[NS_SIDE_TOP] = spreadDistance;
+        borderSizes[NS_SIDE_RIGHT] = spreadDistance;
+        borderSizes[NS_SIDE_BOTTOM] = spreadDistance;
+
+        nsCSSBorderRenderer::ComputeOuterRadii(borderRadii, borderSizes,
+            &clipRectRadii);
+
+      }
+      nsContextBoxBlur::BlurRectangle(renderContext,
+                                      shadowRect,
+                                      twipsPerPixel,
+                                      hasBorderRadius ? &clipRectRadii : nullptr,
+                                      blurRadius,
+                                      gfxShadowColor,
+                                      aDirtyRect,
+                                      skipGfxRect);
+      renderContext->Restore();
+    }
+
+  }
+}
+
+void
+nsCSSRendering::PaintBoxShadowInner(nsPresContext* aPresContext,
+                                    nsRenderingContext& aRenderingContext,
+                                    nsIFrame* aForFrame,
+                                    const nsRect& aFrameArea)
+{
+  nsCSSShadowArray* shadows = aForFrame->StyleEffects()->mBoxShadow;
+  if (!shadows)
+    return;
+  if (aForFrame->IsThemed() && aForFrame->GetContent() &&
+      !nsContentUtils::IsChromeDoc(aForFrame->GetContent()->GetUncomposedDoc())) {
+    // There's no way of getting hold of a shape corresponding to a
+    // "padding-box" for native-themed widgets, so just don't draw
+    // inner box-shadows for them. But we allow chrome to paint inner
+    // box shadows since chrome can be aware of the platform theme.
+    return;
+  }
+
+  NS_ASSERTION(aForFrame->GetType() == nsGkAtoms::fieldSetFrame ||
+               aFrameArea.Size() == aForFrame->GetSize(), "unexpected size");
+
+  Sides skipSides = aForFrame->GetSkipSides();
+  nsRect frameRect =
+    ::BoxDecorationRectForBorder(aForFrame, aFrameArea, skipSides);
+  nsRect paddingRect = frameRect;
+  nsMargin border = aForFrame->GetUsedBorder();
+  paddingRect.Deflate(border);
+
+  // Get any border radius, since box-shadow must also have rounded corners
+  // if the frame does.
+  nscoord twipsRadii[8];
+  nsSize sz = frameRect.Size();
+  bool hasBorderRadius = aForFrame->GetBorderRadii(sz, sz, Sides(), twipsRadii);
+  const nscoord twipsPerPixel = aPresContext->DevPixelsToAppUnits(1);
+
+  RectCornerRadii innerRadii;
+  if (hasBorderRadius) {
+    RectCornerRadii borderRadii;
+
+    ComputePixelRadii(twipsRadii, twipsPerPixel, &borderRadii);
+    Float borderSizes[4] = {
+      Float(border.top / twipsPerPixel),
+      Float(border.right / twipsPerPixel),
+      Float(border.bottom / twipsPerPixel),
+      Float(border.left / twipsPerPixel)
+    };
+    nsCSSBorderRenderer::ComputeInnerRadii(borderRadii, borderSizes,
+                                           &innerRadii);
+  }
+
+  for (uint32_t i = shadows->Length(); i > 0; --i) {
+    nsCSSShadowItem* shadowItem = shadows->ShadowAt(i - 1);
+    if (!shadowItem->mInset)
+      continue;
+
+    // shadowPaintRect: the area to paint on the temp surface
+    // shadowClipRect: the area on the temporary surface within shadowPaintRect
+    //                 that we will NOT paint in
+    nscoord blurRadius = shadowItem->mRadius;
+    nsMargin blurMargin =
+      nsContextBoxBlur::GetBlurRadiusMargin(blurRadius, twipsPerPixel);
+    nsRect shadowPaintRect = paddingRect;
+    shadowPaintRect.Inflate(blurMargin);
+
+    Rect shadowPaintGfxRect = NSRectToRect(shadowPaintRect, twipsPerPixel);
+    shadowPaintGfxRect.RoundOut();
+
+    // Round the spread radius to device pixels (by truncation).
+    // This mostly matches what we do for borders, except that we don't round
+    // up values between zero and one device pixels to one device pixel.
+    // This way of rounding is symmetric around zero, which makes sense for
+    // the spread radius.
+    int32_t spreadDistance = shadowItem->mSpread / twipsPerPixel;
+    nscoord spreadDistanceAppUnits = aPresContext->DevPixelsToAppUnits(spreadDistance);
+
+    nsRect shadowClipRect = paddingRect;
+    shadowClipRect.MoveBy(shadowItem->mXOffset, shadowItem->mYOffset);
+    shadowClipRect.Deflate(spreadDistanceAppUnits, spreadDistanceAppUnits);
+
+    Rect shadowClipGfxRect = NSRectToRect(shadowClipRect, twipsPerPixel);
+    shadowClipGfxRect.Round();
+
+    RectCornerRadii clipRectRadii;
+    if (hasBorderRadius) {
+      // Calculate the radii the inner clipping rect will have
+      Float borderSizes[4] = {0, 0, 0, 0};
+
+      // See PaintBoxShadowOuter and bug 514670
+      if (innerRadii[C_TL].width > 0 || innerRadii[C_BL].width > 0) {
+        borderSizes[NS_SIDE_LEFT] = spreadDistance;
+      }
+
+      if (innerRadii[C_TL].height > 0 || innerRadii[C_TR].height > 0) {
+        borderSizes[NS_SIDE_TOP] = spreadDistance;
+      }
+
+      if (innerRadii[C_TR].width > 0 || innerRadii[C_BR].width > 0) {
+        borderSizes[NS_SIDE_RIGHT] = spreadDistance;
+      }
+
+      if (innerRadii[C_BL].height > 0 || innerRadii[C_BR].height > 0) {
+        borderSizes[NS_SIDE_BOTTOM] = spreadDistance;
+      }
+
+      nsCSSBorderRenderer::ComputeInnerRadii(innerRadii, borderSizes,
+                                             &clipRectRadii);
+    }
+
+    // Set the "skip rect" to the area within the frame that we don't paint in,
+    // including after blurring.
+    nsRect skipRect = shadowClipRect;
+    skipRect.Deflate(blurMargin);
+    gfxRect skipGfxRect = nsLayoutUtils::RectToGfxRect(skipRect, twipsPerPixel);
+    if (hasBorderRadius) {
+      skipGfxRect.Deflate(gfxMargin(
+          std::max(clipRectRadii[C_TL].height, clipRectRadii[C_TR].height), 0,
+          std::max(clipRectRadii[C_BL].height, clipRectRadii[C_BR].height), 0));
+    }
+
+    // When there's a blur radius, gfxAlphaBoxBlur leaves the skiprect area
+    // unchanged. And by construction the gfxSkipRect is not touched by the
+    // rendered shadow (even after blurring), so those pixels must be completely
+    // transparent in the shadow, so drawing them changes nothing.
+    gfxContext* renderContext = aRenderingContext.ThebesContext();
+    DrawTarget* drawTarget = renderContext->GetDrawTarget();
+    nsContextBoxBlur blurringArea;
+
+    // Clip the context to the area of the frame's padding rect, so no part of the
+    // shadow is painted outside. Also cut out anything beyond where the inset shadow
+    // will be.
+    Rect shadowGfxRect = NSRectToRect(paddingRect, twipsPerPixel);
+    shadowGfxRect.Round();
+
+    // Set the shadow color; if not specified, use the foreground color
+    Color shadowColor = Color::FromABGR(shadowItem->mHasColor ?
+                                          shadowItem->mColor :
+                                          aForFrame->StyleColor()->mColor);
+
+    renderContext->Save();
+
+    // This clips the outside border radius.
+    // clipRectRadii is the border radius inside the inset shadow.
+    if (hasBorderRadius) {
+      RefPtr<Path> roundedRect =
+        MakePathForRoundedRect(*drawTarget, shadowGfxRect, innerRadii);
+      renderContext->Clip(roundedRect);
+    } else {
+      renderContext->Clip(shadowGfxRect);
+    }
+
+    nsContextBoxBlur insetBoxBlur;
+    gfxRect destRect = nsLayoutUtils::RectToGfxRect(shadowPaintRect, twipsPerPixel);
+    Point shadowOffset(shadowItem->mXOffset / twipsPerPixel,
+                       shadowItem->mYOffset / twipsPerPixel);
+
+    insetBoxBlur.InsetBoxBlur(renderContext, ToRect(destRect),
+                              shadowClipGfxRect, shadowColor,
+                              blurRadius, spreadDistanceAppUnits,
+                              twipsPerPixel, hasBorderRadius,
+                              clipRectRadii, ToRect(skipGfxRect),
+                              shadowOffset);
+    renderContext->Restore();
+  }
+}
+
+/* static */
+nsCSSRendering::PaintBGParams
+nsCSSRendering::PaintBGParams::ForAllLayers(nsPresContext& aPresCtx,
+                                            nsRenderingContext& aRenderingCtx,
+                                            const nsRect& aDirtyRect,
+                                            const nsRect& aBorderArea,
+                                            nsIFrame *aFrame,
+                                            uint32_t aPaintFlags)
+{
+  MOZ_ASSERT(aFrame);
+
+  PaintBGParams result(aPresCtx, aRenderingCtx, aDirtyRect, aBorderArea, aFrame,
+    aPaintFlags, -1, CompositionOp::OP_OVER);
+
+  return result;
+}
+
+/* static */
+nsCSSRendering::PaintBGParams
+nsCSSRendering::PaintBGParams::ForSingleLayer(nsPresContext& aPresCtx,
+                                              nsRenderingContext& aRenderingCtx,
+                                              const nsRect& aDirtyRect,
+                                              const nsRect& aBorderArea,
+                                              nsIFrame *aFrame,
+                                              uint32_t aPaintFlags,
+                                              int32_t aLayer,
+                                              CompositionOp aCompositionOp)
+{
+  MOZ_ASSERT(aFrame && (aLayer != -1));
+
+  PaintBGParams result(aPresCtx, aRenderingCtx, aDirtyRect, aBorderArea, aFrame,
+    aPaintFlags, aLayer, aCompositionOp);
+
+  return result;
+}
+
+DrawResult
+nsCSSRendering::PaintBackground(const PaintBGParams& aParams)
+{
+  PROFILER_LABEL("nsCSSRendering", "PaintBackground",
+    js::ProfileEntry::Category::GRAPHICS);
+
+  NS_PRECONDITION(aParams.frame,
+                  "Frame is expected to be provided to PaintBackground");
+
+  nsStyleContext *sc;
+  if (!FindBackground(aParams.frame, &sc)) {
+    // We don't want to bail out if moz-appearance is set on a root
+    // node. If it has a parent content node, bail because it's not
+    // a root, otherwise keep going in order to let the theme stuff
+    // draw the background. The canvas really should be drawing the
+    // bg, but there's no way to hook that up via css.
+    if (!aParams.frame->StyleDisplay()->mAppearance) {
+      return DrawResult::SUCCESS;
+    }
+
+    nsIContent* content = aParams.frame->GetContent();
+    if (!content || content->GetParent()) {
+      return DrawResult::SUCCESS;
+    }
+
+    sc = aParams.frame->StyleContext();
+  }
+
+  return PaintBackgroundWithSC(aParams, sc, *aParams.frame->StyleBorder());
+}
+
+static bool
+IsOpaqueBorderEdge(const nsStyleBorder& aBorder, mozilla::css::Side aSide)
+{
+  if (aBorder.GetComputedBorder().Side(aSide) == 0)
+    return true;
+  switch (aBorder.GetBorderStyle(aSide)) {
+  case NS_STYLE_BORDER_STYLE_SOLID:
+  case NS_STYLE_BORDER_STYLE_GROOVE:
+  case NS_STYLE_BORDER_STYLE_RIDGE:
+  case NS_STYLE_BORDER_STYLE_INSET:
+  case NS_STYLE_BORDER_STYLE_OUTSET:
+    break;
+  default:
+    return false;
+  }
+
+  // If we're using a border image, assume it's not fully opaque,
+  // because we may not even have the image loaded at this point, and
+  // even if we did, checking whether the relevant tile is fully
+  // opaque would be too much work.
+  if (aBorder.mBorderImageSource.GetType() != eStyleImageType_Null)
+    return false;
+
+  StyleComplexColor color = aBorder.mBorderColor[aSide];
+  // We don't know the foreground color here, so if it's being used
+  // we must assume it might be transparent.
+  if (!color.IsNumericColor()) {
+    return false;
+  }
+  return NS_GET_A(color.mColor) == 255;
+}
+
+/**
+ * Returns true if all border edges are either missing or opaque.
+ */
+static bool
+IsOpaqueBorder(const nsStyleBorder& aBorder)
+{
+  if (aBorder.mBorderColors)
+    return false;
+  NS_FOR_CSS_SIDES(i) {
+    if (!IsOpaqueBorderEdge(aBorder, i))
+      return false;
+  }
+  return true;
+}
+
+static inline void
+SetupDirtyRects(const nsRect& aBGClipArea, const nsRect& aCallerDirtyRect,
+                nscoord aAppUnitsPerPixel,
+                /* OUT: */
+                nsRect* aDirtyRect, gfxRect* aDirtyRectGfx)
+{
+  aDirtyRect->IntersectRect(aBGClipArea, aCallerDirtyRect);
+
+  // Compute the Thebes equivalent of the dirtyRect.
+  *aDirtyRectGfx = nsLayoutUtils::RectToGfxRect(*aDirtyRect, aAppUnitsPerPixel);
+  NS_WARNING_ASSERTION(aDirtyRect->IsEmpty() || !aDirtyRectGfx->IsEmpty(),
+                       "converted dirty rect should not be empty");
+  MOZ_ASSERT(!aDirtyRect->IsEmpty() || aDirtyRectGfx->IsEmpty(),
+             "second should be empty if first is");
+}
+
+/* static */ void
+nsCSSRendering::GetImageLayerClip(const nsStyleImageLayers::Layer& aLayer,
+                                  nsIFrame* aForFrame, const nsStyleBorder& aBorder,
+                                  const nsRect& aBorderArea, const nsRect& aCallerDirtyRect,
+                                  bool aWillPaintBorder, nscoord aAppUnitsPerPixel,
+                                  /* out */ ImageLayerClipState* aClipState)
+{
+  // Compute the outermost boundary of the area that might be painted.
+  // Same coordinate space as aBorderArea.
+  Sides skipSides = aForFrame->GetSkipSides();
+  nsRect clipBorderArea =
+    ::BoxDecorationRectForBorder(aForFrame, aBorderArea, skipSides, &aBorder);
+
+  bool haveRoundedCorners = GetRadii(aForFrame, aBorder, aBorderArea,
+                                     clipBorderArea, aClipState->mRadii);
+
+  uint8_t backgroundClip = aLayer.mClip;
+
+  bool isSolidBorder =
+      aWillPaintBorder && IsOpaqueBorder(aBorder);
+  if (isSolidBorder && backgroundClip == NS_STYLE_IMAGELAYER_CLIP_BORDER) {
+    // If we have rounded corners, we need to inflate the background
+    // drawing area a bit to avoid seams between the border and
+    // background.
+    backgroundClip = haveRoundedCorners ?
+      NS_STYLE_IMAGELAYER_CLIP_MOZ_ALMOST_PADDING : NS_STYLE_IMAGELAYER_CLIP_PADDING;
+  }
+
+  aClipState->mBGClipArea = clipBorderArea;
+  aClipState->mHasAdditionalBGClipArea = false;
+  aClipState->mCustomClip = false;
+
+  if (aForFrame->GetType() == nsGkAtoms::scrollFrame &&
+      NS_STYLE_IMAGELAYER_ATTACHMENT_LOCAL == aLayer.mAttachment) {
+    // As of this writing, this is still in discussion in the CSS Working Group
+    // http://lists.w3.org/Archives/Public/www-style/2013Jul/0250.html
+
+    // The rectangle for 'background-clip' scrolls with the content,
+    // but the background is also clipped at a non-scrolling 'padding-box'
+    // like the content. (See below.)
+    // Therefore, only 'content-box' makes a difference here.
+    if (backgroundClip == NS_STYLE_IMAGELAYER_CLIP_CONTENT) {
+      nsIScrollableFrame* scrollableFrame = do_QueryFrame(aForFrame);
+      // Clip at a rectangle attached to the scrolled content.
+      aClipState->mHasAdditionalBGClipArea = true;
+      aClipState->mAdditionalBGClipArea = nsRect(
+        aClipState->mBGClipArea.TopLeft()
+          + scrollableFrame->GetScrolledFrame()->GetPosition()
+          // For the dir=rtl case:
+          + scrollableFrame->GetScrollRange().TopLeft(),
+        scrollableFrame->GetScrolledRect().Size());
+      nsMargin padding = aForFrame->GetUsedPadding();
+      // padding-bottom is ignored on scrollable frames:
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=748518
+      padding.bottom = 0;
+      padding.ApplySkipSides(skipSides);
+      aClipState->mAdditionalBGClipArea.Deflate(padding);
+    }
+
+    // Also clip at a non-scrolling, rounded-corner 'padding-box',
+    // same as the scrolled content because of the 'overflow' property.
+    backgroundClip = NS_STYLE_IMAGELAYER_CLIP_PADDING;
+  }
+
+  if (backgroundClip != NS_STYLE_IMAGELAYER_CLIP_BORDER &&
+      backgroundClip != NS_STYLE_IMAGELAYER_CLIP_TEXT) {
+    nsMargin border = aForFrame->GetUsedBorder();
+    if (backgroundClip == NS_STYLE_IMAGELAYER_CLIP_MOZ_ALMOST_PADDING) {
+      // Reduce |border| by 1px (device pixels) on all sides, if
+      // possible, so that we don't get antialiasing seams between the
+      // background and border.
+      border.top = std::max(0, border.top - aAppUnitsPerPixel);
+      border.right = std::max(0, border.right - aAppUnitsPerPixel);
+      border.bottom = std::max(0, border.bottom - aAppUnitsPerPixel);
+      border.left = std::max(0, border.left - aAppUnitsPerPixel);
+    } else if (backgroundClip != NS_STYLE_IMAGELAYER_CLIP_PADDING) {
+      NS_ASSERTION(backgroundClip == NS_STYLE_IMAGELAYER_CLIP_CONTENT,
+                   "unexpected background-clip");
+      border += aForFrame->GetUsedPadding();
+    }
+    border.ApplySkipSides(skipSides);
+    aClipState->mBGClipArea.Deflate(border);
+
+    if (haveRoundedCorners) {
+      nsIFrame::InsetBorderRadii(aClipState->mRadii, border);
+    }
+  }
+
+  if (haveRoundedCorners) {
+    auto d2a = aForFrame->PresContext()->AppUnitsPerDevPixel();
+    nsCSSRendering::ComputePixelRadii(aClipState->mRadii, d2a, &aClipState->mClippedRadii);
+    aClipState->mHasRoundedCorners = true;
+  } else {
+    aClipState->mHasRoundedCorners = false;
+  }
+
+
+  if (!haveRoundedCorners && aClipState->mHasAdditionalBGClipArea) {
+    // Do the intersection here to account for the fast path(?) below.
+    aClipState->mBGClipArea =
+      aClipState->mBGClipArea.Intersect(aClipState->mAdditionalBGClipArea);
+    aClipState->mHasAdditionalBGClipArea = false;
+  }
+
+  SetupDirtyRects(aClipState->mBGClipArea, aCallerDirtyRect, aAppUnitsPerPixel,
+                  &aClipState->mDirtyRect, &aClipState->mDirtyRectGfx);
+}
+
+static void
+SetupImageLayerClip(nsCSSRendering::ImageLayerClipState& aClipState,
+                    gfxContext *aCtx, nscoord aAppUnitsPerPixel,
+                    gfxContextAutoSaveRestore* aAutoSR)
+{
+  if (aClipState.mDirtyRectGfx.IsEmpty()) {
+    // Our caller won't draw anything under this condition, so no need
+    // to set more up.
+    return;
+  }
+
+  if (aClipState.mCustomClip) {
+    // We don't support custom clips and rounded corners, arguably a bug, but
+    // table painting seems to depend on it.
+    return;
+  }
+
+  DrawTarget* drawTarget = aCtx->GetDrawTarget();
+
+  // If we have rounded corners, clip all subsequent drawing to the
+  // rounded rectangle defined by bgArea and bgRadii (we don't know
+  // whether the rounded corners intrude on the dirtyRect or not).
+  // Do not do this if we have a caller-provided clip rect --
+  // as above with bgArea, arguably a bug, but table painting seems
+  // to depend on it.
+
+  if (aClipState.mHasAdditionalBGClipArea) {
+    gfxRect bgAreaGfx = nsLayoutUtils::RectToGfxRect(
+      aClipState.mAdditionalBGClipArea, aAppUnitsPerPixel);
+    bgAreaGfx.Round();
+    bgAreaGfx.Condition();
+
+    aAutoSR->EnsureSaved(aCtx);
+    aCtx->NewPath();
+    aCtx->Rectangle(bgAreaGfx, true);
+    aCtx->Clip();
+  }
+
+  if (aClipState.mHasRoundedCorners) {
+    Rect bgAreaGfx = NSRectToRect(aClipState.mBGClipArea, aAppUnitsPerPixel);
+    bgAreaGfx.Round();
+
+    if (bgAreaGfx.IsEmpty()) {
+      // I think it's become possible to hit this since
+      // http://hg.mozilla.org/mozilla-central/rev/50e934e4979b landed.
+      NS_WARNING("converted background area should not be empty");
+      // Make our caller not do anything.
+      aClipState.mDirtyRectGfx.SizeTo(gfxSize(0.0, 0.0));
+      return;
+    }
+
+    aAutoSR->EnsureSaved(aCtx);
+
+    RefPtr<Path> roundedRect =
+      MakePathForRoundedRect(*drawTarget, bgAreaGfx, aClipState.mClippedRadii);
+    aCtx->Clip(roundedRect);
+  }
+}
+
+static void
+DrawBackgroundColor(nsCSSRendering::ImageLayerClipState& aClipState,
+                    gfxContext *aCtx, nscoord aAppUnitsPerPixel)
+{
+  if (aClipState.mDirtyRectGfx.IsEmpty()) {
+    // Our caller won't draw anything under this condition, so no need
+    // to set more up.
+    return;
+  }
+
+  DrawTarget* drawTarget = aCtx->GetDrawTarget();
+
+  // We don't support custom clips and rounded corners, arguably a bug, but
+  // table painting seems to depend on it.
+  if (!aClipState.mHasRoundedCorners || aClipState.mCustomClip) {
+    aCtx->NewPath();
+    aCtx->Rectangle(aClipState.mDirtyRectGfx, true);
+    aCtx->Fill();
+    return;
+  }
+
+  Rect bgAreaGfx = NSRectToRect(aClipState.mBGClipArea, aAppUnitsPerPixel);
+  bgAreaGfx.Round();
+
+  if (bgAreaGfx.IsEmpty()) {
+    // I think it's become possible to hit this since
+    // http://hg.mozilla.org/mozilla-central/rev/50e934e4979b landed.
+    NS_WARNING("converted background area should not be empty");
+    // Make our caller not do anything.
+    aClipState.mDirtyRectGfx.SizeTo(gfxSize(0.0, 0.0));
+    return;
+  }
+
+  aCtx->Save();
+  gfxRect dirty = ThebesRect(bgAreaGfx).Intersect(aClipState.mDirtyRectGfx);
+
+  aCtx->NewPath();
+  aCtx->Rectangle(dirty, true);
+  aCtx->Clip();
+
+  if (aClipState.mHasAdditionalBGClipArea) {
+    gfxRect bgAdditionalAreaGfx = nsLayoutUtils::RectToGfxRect(
+      aClipState.mAdditionalBGClipArea, aAppUnitsPerPixel);
+    bgAdditionalAreaGfx.Round();
+    bgAdditionalAreaGfx.Condition();
+    aCtx->NewPath();
+    aCtx->Rectangle(bgAdditionalAreaGfx, true);
+    aCtx->Clip();
+  }
+
+  RefPtr<Path> roundedRect =
+    MakePathForRoundedRect(*drawTarget, bgAreaGfx, aClipState.mClippedRadii);
+  aCtx->SetPath(roundedRect);
+  aCtx->Fill();
+  aCtx->Restore();
+}
+
+nscolor
+nsCSSRendering::DetermineBackgroundColor(nsPresContext* aPresContext,
+                                         nsStyleContext* aStyleContext,
+                                         nsIFrame* aFrame,
+                                         bool& aDrawBackgroundImage,
+                                         bool& aDrawBackgroundColor)
+{
+  aDrawBackgroundImage = true;
+  aDrawBackgroundColor = true;
+
+  const nsStyleVisibility* visibility = aStyleContext->StyleVisibility();
+
+  if (visibility->mColorAdjust != NS_STYLE_COLOR_ADJUST_EXACT &&
+      aFrame->HonorPrintBackgroundSettings()) {
+    aDrawBackgroundImage = aPresContext->GetBackgroundImageDraw();
+    aDrawBackgroundColor = aPresContext->GetBackgroundColorDraw();
+  }
+
+  const nsStyleBackground *bg = aStyleContext->StyleBackground();
+  nscolor bgColor;
+  if (aDrawBackgroundColor) {
+    bgColor =
+      aStyleContext->GetVisitedDependentColor(eCSSProperty_background_color);
+    if (NS_GET_A(bgColor) == 0) {
+      aDrawBackgroundColor = false;
+    }
+  } else {
+    // If GetBackgroundColorDraw() is false, we are still expected to
+    // draw color in the background of any frame that's not completely
+    // transparent, but we are expected to use white instead of whatever
+    // color was specified.
+    bgColor = NS_RGB(255, 255, 255);
+    if (aDrawBackgroundImage || !bg->IsTransparent()) {
+      aDrawBackgroundColor = true;
+    } else {
+      bgColor = NS_RGBA(0,0,0,0);
+    }
+  }
+
+  // We can skip painting the background color if a background image is opaque.
+  nsStyleImageLayers::Repeat repeat = bg->BottomLayer().mRepeat;
+  bool xFullRepeat = repeat.mXRepeat == NS_STYLE_IMAGELAYER_REPEAT_REPEAT ||
+                     repeat.mXRepeat == NS_STYLE_IMAGELAYER_REPEAT_ROUND;
+  bool yFullRepeat = repeat.mYRepeat == NS_STYLE_IMAGELAYER_REPEAT_REPEAT ||
+                     repeat.mYRepeat == NS_STYLE_IMAGELAYER_REPEAT_ROUND;
+  if (aDrawBackgroundColor &&
+      xFullRepeat && yFullRepeat &&
+      bg->BottomLayer().mImage.IsOpaque() &&
+      bg->BottomLayer().mBlendMode == NS_STYLE_BLEND_NORMAL) {
+    aDrawBackgroundColor = false;
+  }
+
+  return bgColor;
+}
+
+static gfxFloat
+ConvertGradientValueToPixels(const nsStyleCoord& aCoord,
+                             gfxFloat aFillLength,
+                             int32_t aAppUnitsPerPixel)
+{
+  switch (aCoord.GetUnit()) {
+    case eStyleUnit_Percent:
+      return aCoord.GetPercentValue() * aFillLength;
+    case eStyleUnit_Coord:
+      return NSAppUnitsToFloatPixels(aCoord.GetCoordValue(), aAppUnitsPerPixel);
+    case eStyleUnit_Calc: {
+      const nsStyleCoord::Calc *calc = aCoord.GetCalcValue();
+      return calc->mPercent * aFillLength +
+             NSAppUnitsToFloatPixels(calc->mLength, aAppUnitsPerPixel);
+    }
+    default:
+      NS_WARNING("Unexpected coord unit");
+      return 0;
+  }
+}
+
+// Given a box with size aBoxSize and origin (0,0), and an angle aAngle,
+// and a starting point for the gradient line aStart, find the endpoint of
+// the gradient line --- the intersection of the gradient line with a line
+// perpendicular to aAngle that passes through the farthest corner in the
+// direction aAngle.
+static gfxPoint
+ComputeGradientLineEndFromAngle(const gfxPoint& aStart,
+                                double aAngle,
+                                const gfxSize& aBoxSize)
+{
+  double dx = cos(-aAngle);
+  double dy = sin(-aAngle);
+  gfxPoint farthestCorner(dx > 0 ? aBoxSize.width : 0,
+                          dy > 0 ? aBoxSize.height : 0);
+  gfxPoint delta = farthestCorner - aStart;
+  double u = delta.x*dy - delta.y*dx;
+  return farthestCorner + gfxPoint(-u*dy, u*dx);
+}
+
+// Compute the start and end points of the gradient line for a linear gradient.
+static void
+ComputeLinearGradientLine(nsPresContext* aPresContext,
+                          nsStyleGradient* aGradient,
+                          const gfxSize& aBoxSize,
+                          gfxPoint* aLineStart,
+                          gfxPoint* aLineEnd)
+{
+  if (aGradient->mBgPosX.GetUnit() == eStyleUnit_None) {
+    double angle;
+    if (aGradient->mAngle.IsAngleValue()) {
+      angle = aGradient->mAngle.GetAngleValueInRadians();
+      if (!aGradient->mLegacySyntax) {
+        angle = M_PI_2 - angle;
+      }
+    } else {
+      angle = -M_PI_2; // defaults to vertical gradient starting from top
+    }
+    gfxPoint center(aBoxSize.width/2, aBoxSize.height/2);
+    *aLineEnd = ComputeGradientLineEndFromAngle(center, angle, aBoxSize);
+    *aLineStart = gfxPoint(aBoxSize.width, aBoxSize.height) - *aLineEnd;
+  } else if (!aGradient->mLegacySyntax) {
+    float xSign = aGradient->mBgPosX.GetPercentValue() * 2 - 1;
+    float ySign = 1 - aGradient->mBgPosY.GetPercentValue() * 2;
+    double angle = atan2(ySign * aBoxSize.width, xSign * aBoxSize.height);
+    gfxPoint center(aBoxSize.width/2, aBoxSize.height/2);
+    *aLineEnd = ComputeGradientLineEndFromAngle(center, angle, aBoxSize);
+    *aLineStart = gfxPoint(aBoxSize.width, aBoxSize.height) - *aLineEnd;
+  } else {
+    int32_t appUnitsPerPixel = aPresContext->AppUnitsPerDevPixel();
+    *aLineStart = gfxPoint(
+      ConvertGradientValueToPixels(aGradient->mBgPosX, aBoxSize.width,
+                                   appUnitsPerPixel),
+      ConvertGradientValueToPixels(aGradient->mBgPosY, aBoxSize.height,
+                                   appUnitsPerPixel));
+    if (aGradient->mAngle.IsAngleValue()) {
+      MOZ_ASSERT(aGradient->mLegacySyntax);
+      double angle = aGradient->mAngle.GetAngleValueInRadians();
+      *aLineEnd = ComputeGradientLineEndFromAngle(*aLineStart, angle, aBoxSize);
+    } else {
+      // No angle, the line end is just the reflection of the start point
+      // through the center of the box
+      *aLineEnd = gfxPoint(aBoxSize.width, aBoxSize.height) - *aLineStart;
+    }
+  }
+}
+
+// Compute the start and end points of the gradient line for a radial gradient.
+// Also returns the horizontal and vertical radii defining the circle or
+// ellipse to use.
+static void
+ComputeRadialGradientLine(nsPresContext* aPresContext,
+                          nsStyleGradient* aGradient,
+                          const gfxSize& aBoxSize,
+                          gfxPoint* aLineStart,
+                          gfxPoint* aLineEnd,
+                          double* aRadiusX,
+                          double* aRadiusY)
+{
+  if (aGradient->mBgPosX.GetUnit() == eStyleUnit_None) {
+    // Default line start point is the center of the box
+    *aLineStart = gfxPoint(aBoxSize.width/2, aBoxSize.height/2);
+  } else {
+    int32_t appUnitsPerPixel = aPresContext->AppUnitsPerDevPixel();
+    *aLineStart = gfxPoint(
+      ConvertGradientValueToPixels(aGradient->mBgPosX, aBoxSize.width,
+                                   appUnitsPerPixel),
+      ConvertGradientValueToPixels(aGradient->mBgPosY, aBoxSize.height,
+                                   appUnitsPerPixel));
+  }
+
+  // Compute gradient shape: the x and y radii of an ellipse.
+  double radiusX, radiusY;
+  double leftDistance = Abs(aLineStart->x);
+  double rightDistance = Abs(aBoxSize.width - aLineStart->x);
+  double topDistance = Abs(aLineStart->y);
+  double bottomDistance = Abs(aBoxSize.height - aLineStart->y);
+  switch (aGradient->mSize) {
+  case NS_STYLE_GRADIENT_SIZE_CLOSEST_SIDE:
+    radiusX = std::min(leftDistance, rightDistance);
+    radiusY = std::min(topDistance, bottomDistance);
+    if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
+      radiusX = radiusY = std::min(radiusX, radiusY);
+    }
+    break;
+  case NS_STYLE_GRADIENT_SIZE_CLOSEST_CORNER: {
+    // Compute x and y distances to nearest corner
+    double offsetX = std::min(leftDistance, rightDistance);
+    double offsetY = std::min(topDistance, bottomDistance);
+    if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
+      radiusX = radiusY = NS_hypot(offsetX, offsetY);
+    } else {
+      // maintain aspect ratio
+      radiusX = offsetX*M_SQRT2;
+      radiusY = offsetY*M_SQRT2;
+    }
+    break;
+  }
+  case NS_STYLE_GRADIENT_SIZE_FARTHEST_SIDE:
+    radiusX = std::max(leftDistance, rightDistance);
+    radiusY = std::max(topDistance, bottomDistance);
+    if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
+      radiusX = radiusY = std::max(radiusX, radiusY);
+    }
+    break;
+  case NS_STYLE_GRADIENT_SIZE_FARTHEST_CORNER: {
+    // Compute x and y distances to nearest corner
+    double offsetX = std::max(leftDistance, rightDistance);
+    double offsetY = std::max(topDistance, bottomDistance);
+    if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
+      radiusX = radiusY = NS_hypot(offsetX, offsetY);
+    } else {
+      // maintain aspect ratio
+      radiusX = offsetX*M_SQRT2;
+      radiusY = offsetY*M_SQRT2;
+    }
+    break;
+  }
+  case NS_STYLE_GRADIENT_SIZE_EXPLICIT_SIZE: {
+    int32_t appUnitsPerPixel = aPresContext->AppUnitsPerDevPixel();
+    radiusX = ConvertGradientValueToPixels(aGradient->mRadiusX,
+                                           aBoxSize.width, appUnitsPerPixel);
+    radiusY = ConvertGradientValueToPixels(aGradient->mRadiusY,
+                                           aBoxSize.height, appUnitsPerPixel);
+    break;
+  }
+  default:
+    radiusX = radiusY = 0;
+    MOZ_ASSERT(false, "unknown radial gradient sizing method");
+  }
+  *aRadiusX = radiusX;
+  *aRadiusY = radiusY;
+
+  double angle;
+  if (aGradient->mAngle.IsAngleValue()) {
+    angle = aGradient->mAngle.GetAngleValueInRadians();
+  } else {
+    // Default angle is 0deg
+    angle = 0.0;
+  }
+
+  // The gradient line end point is where the gradient line intersects
+  // the ellipse.
+  *aLineEnd = *aLineStart + gfxPoint(radiusX*cos(-angle), radiusY*sin(-angle));
+}
+
+
+static float Interpolate(float aF1, float aF2, float aFrac)
+{
+  return aF1 + aFrac * (aF2 - aF1);
+}
+
+// Returns aFrac*aC2 + (1 - aFrac)*C1. The interpolation is done
+// in unpremultiplied space, which is what SVG gradients and cairo
+// gradients expect.
+static Color
+InterpolateColor(const Color& aC1, const Color& aC2, float aFrac)
+{
+  double other = 1 - aFrac;
+  return Color(aC2.r*aFrac + aC1.r*other,
+               aC2.g*aFrac + aC1.g*other,
+               aC2.b*aFrac + aC1.b*other,
+               aC2.a*aFrac + aC1.a*other);
+}
+
+static nscoord
+FindTileStart(nscoord aDirtyCoord, nscoord aTilePos, nscoord aTileDim)
+{
+  NS_ASSERTION(aTileDim > 0, "Non-positive tile dimension");
+  double multiples = floor(double(aDirtyCoord - aTilePos)/aTileDim);
+  return NSToCoordRound(multiples*aTileDim + aTilePos);
+}
+
+static gfxFloat
+LinearGradientStopPositionForPoint(const gfxPoint& aGradientStart,
+                                   const gfxPoint& aGradientEnd,
+                                   const gfxPoint& aPoint)
+{
+  gfxPoint d = aGradientEnd - aGradientStart;
+  gfxPoint p = aPoint - aGradientStart;
+  /**
+   * Compute a parameter t such that a line perpendicular to the
+   * d vector, passing through aGradientStart + d*t, also
+   * passes through aPoint.
+   *
+   * t is given by
+   *   (p.x - d.x*t)*d.x + (p.y - d.y*t)*d.y = 0
+   *
+   * Solving for t we get
+   *   numerator = d.x*p.x + d.y*p.y
+   *   denominator = d.x^2 + d.y^2
+   *   t = numerator/denominator
+   *
+   * In nsCSSRendering::PaintGradient we know the length of d
+   * is not zero.
+   */
+  double numerator = d.x * p.x + d.y * p.y;
+  double denominator = d.x * d.x + d.y * d.y;
+  return numerator / denominator;
+}
+
+static bool
+RectIsBeyondLinearGradientEdge(const gfxRect& aRect,
+                               const gfxMatrix& aPatternMatrix,
+                               const nsTArray<ColorStop>& aStops,
+                               const gfxPoint& aGradientStart,
+                               const gfxPoint& aGradientEnd,
+                               Color* aOutEdgeColor)
+{
+  gfxFloat topLeft = LinearGradientStopPositionForPoint(
+    aGradientStart, aGradientEnd, aPatternMatrix.Transform(aRect.TopLeft()));
+  gfxFloat topRight = LinearGradientStopPositionForPoint(
+    aGradientStart, aGradientEnd, aPatternMatrix.Transform(aRect.TopRight()));
+  gfxFloat bottomLeft = LinearGradientStopPositionForPoint(
+    aGradientStart, aGradientEnd, aPatternMatrix.Transform(aRect.BottomLeft()));
+  gfxFloat bottomRight = LinearGradientStopPositionForPoint(
+    aGradientStart, aGradientEnd, aPatternMatrix.Transform(aRect.BottomRight()));
+
+  const ColorStop& firstStop = aStops[0];
+  if (topLeft < firstStop.mPosition && topRight < firstStop.mPosition &&
+      bottomLeft < firstStop.mPosition && bottomRight < firstStop.mPosition) {
+    *aOutEdgeColor = firstStop.mColor;
+    return true;
+  }
+
+  const ColorStop& lastStop = aStops.LastElement();
+  if (topLeft >= lastStop.mPosition && topRight >= lastStop.mPosition &&
+      bottomLeft >= lastStop.mPosition && bottomRight >= lastStop.mPosition) {
+    *aOutEdgeColor = lastStop.mColor;
+    return true;
+  }
+
+  return false;
+}
+
+static void ResolveMidpoints(nsTArray<ColorStop>& stops)
+{
+  for (size_t x = 1; x < stops.Length() - 1;) {
+    if (!stops[x].mIsMidpoint) {
+      x++;
+      continue;
+    }
+
+    Color color1 = stops[x-1].mColor;
+    Color color2 = stops[x+1].mColor;
+    float offset1 = stops[x-1].mPosition;
+    float offset2 = stops[x+1].mPosition;
+    float offset = stops[x].mPosition;
+    // check if everything coincides. If so, ignore the midpoint.
+    if (offset - offset1 == offset2 - offset) {
+      stops.RemoveElementAt(x);
+      continue;
+    }
+
+    // Check if we coincide with the left colorstop.
+    if (offset1 == offset) {
+      // Morph the midpoint to a regular stop with the color of the next
+      // color stop.
+      stops[x].mColor = color2;
+      stops[x].mIsMidpoint = false;
+      continue;
+    }
+
+    // Check if we coincide with the right colorstop.
+    if (offset2 == offset) {
+      // Morph the midpoint to a regular stop with the color of the previous
+      // color stop.
+      stops[x].mColor = color1;
+      stops[x].mIsMidpoint = false;
+      continue;
+    }
+
+    float midpoint = (offset - offset1) / (offset2 - offset1);
+    ColorStop newStops[9];
+    if (midpoint > .5f) {
+      for (size_t y = 0; y < 7; y++) {
+        newStops[y].mPosition = offset1 + (offset - offset1) * (7 + y) / 13;
+      }
+
+      newStops[7].mPosition = offset + (offset2 - offset) / 3;
+      newStops[8].mPosition = offset + (offset2 - offset) * 2 / 3;
+    } else {
+      newStops[0].mPosition = offset1 + (offset - offset1) / 3;
+      newStops[1].mPosition = offset1 + (offset - offset1) * 2 / 3;
+
+      for (size_t y = 0; y < 7; y++) {
+        newStops[y+2].mPosition = offset + (offset2 - offset) * y / 13;
+      }
+    }
+    // calculate colors
+
+    for (size_t y = 0; y < 9; y++) {
+      // Calculate the intermediate color stops per the formula of the CSS images
+      // spec. http://dev.w3.org/csswg/css-images/#color-stop-syntax
+      // 9 points were chosen since it is the minimum number of stops that always
+      // give the smoothest appearace regardless of midpoint position and difference
+      // in luminance of the end points.
+      float relativeOffset = (newStops[y].mPosition - offset1) / (offset2 - offset1);
+      float multiplier = powf(relativeOffset, logf(.5f) / logf(midpoint));
+
+      gfx::Float red = color1.r + multiplier * (color2.r - color1.r);
+      gfx::Float green = color1.g + multiplier * (color2.g - color1.g);
+      gfx::Float blue = color1.b + multiplier * (color2.b - color1.b);
+      gfx::Float alpha = color1.a + multiplier * (color2.a - color1.a);
+
+      newStops[y].mColor = Color(red, green, blue, alpha);
+    }
+
+    stops.ReplaceElementsAt(x, 1, newStops, 9);
+    x += 9;
+  }
+}
+
+static Color
+Premultiply(const Color& aColor)
+{
+  gfx::Float a = aColor.a;
+  return Color(aColor.r * a, aColor.g * a, aColor.b * a, a);
+}
+
+static Color
+Unpremultiply(const Color& aColor)
+{
+  gfx::Float a = aColor.a;
+  return (a > 0.f)
+       ? Color(aColor.r / a, aColor.g / a, aColor.b / a, a)
+       : aColor;
+}
+
+static Color
+TransparentColor(Color aColor) {
+  aColor.a = 0;
+  return aColor;
+}
+
+// Adjusts and adds color stops in such a way that drawing the gradient with
+// unpremultiplied interpolation looks nearly the same as if it were drawn with
+// premultiplied interpolation.
+static const float kAlphaIncrementPerGradientStep = 0.1f;
+static void
+ResolvePremultipliedAlpha(nsTArray<ColorStop>& aStops)
+{
+  for (size_t x = 1; x < aStops.Length(); x++) {
+    const ColorStop leftStop = aStops[x - 1];
+    const ColorStop rightStop = aStops[x];
+
+    // if the left and right stop have the same alpha value, we don't need
+    // to do anything
+    if (leftStop.mColor.a == rightStop.mColor.a) {
+      continue;
+    }
+
+    // Is the stop on the left 100% transparent? If so, have it adopt the color
+    // of the right stop
+    if (leftStop.mColor.a == 0) {
+      aStops[x - 1].mColor = TransparentColor(rightStop.mColor);
+      continue;
+    }
+
+    // Is the stop on the right completely transparent?
+    // If so, duplicate it and assign it the color on the left.
+    if (rightStop.mColor.a == 0) {
+      ColorStop newStop = rightStop;
+      newStop.mColor = TransparentColor(leftStop.mColor);
+      aStops.InsertElementAt(x, newStop);
+      x++;
+      continue;
+    }
+
+    // Now handle cases where one or both of the stops are partially transparent.
+    if (leftStop.mColor.a != 1.0f || rightStop.mColor.a != 1.0f) {
+      Color premulLeftColor = Premultiply(leftStop.mColor);
+      Color premulRightColor = Premultiply(rightStop.mColor);
+      // Calculate how many extra steps. We do a step per 10% transparency.
+      size_t stepCount = NSToIntFloor(fabsf(leftStop.mColor.a - rightStop.mColor.a) / kAlphaIncrementPerGradientStep);
+      for (size_t y = 1; y < stepCount; y++) {
+        float frac = static_cast<float>(y) / stepCount;
+        ColorStop newStop(Interpolate(leftStop.mPosition, rightStop.mPosition, frac), false,
+                          Unpremultiply(InterpolateColor(premulLeftColor, premulRightColor, frac)));
+        aStops.InsertElementAt(x, newStop);
+        x++;
+      }
+    }
+  }
+}
+
+static ColorStop
+InterpolateColorStop(const ColorStop& aFirst, const ColorStop& aSecond,
+                     double aPosition, const Color& aDefault)
+{
+  MOZ_ASSERT(aFirst.mPosition <= aPosition);
+  MOZ_ASSERT(aPosition <= aSecond.mPosition);
+
+  double delta = aSecond.mPosition - aFirst.mPosition;
+
+  if (delta < 1e-6) {
+    return ColorStop(aPosition, false, aDefault);
+  }
+
+  return ColorStop(aPosition, false,
+                   Unpremultiply(InterpolateColor(Premultiply(aFirst.mColor),
+                                                  Premultiply(aSecond.mColor),
+                                                  (aPosition - aFirst.mPosition) / delta)));
+}
+
+// Clamp and extend the given ColorStop array in-place to fit exactly into the
+// range [0, 1].
+static void
+ClampColorStops(nsTArray<ColorStop>& aStops)
+{
+  MOZ_ASSERT(aStops.Length() > 0);
+
+  // If all stops are outside the range, then get rid of everything and replace
+  // with a single colour.
+  if (aStops.Length() < 2 || aStops[0].mPosition > 1 ||
+      aStops.LastElement().mPosition < 0) {
+    Color c = aStops[0].mPosition > 1 ? aStops[0].mColor : aStops.LastElement().mColor;
+    aStops.Clear();
+    aStops.AppendElement(ColorStop(0, false, c));
+    return;
+  }
+
+  // Create the 0 and 1 points if they fall in the range of |aStops|, and discard
+  // all stops outside the range [0, 1].
+  // XXX: If we have stops positioned at 0 or 1, we only keep the innermost of
+  // those stops. This should be fine for the current user(s) of this function.
+  for (size_t i = aStops.Length() - 1; i > 0; i--) {
+    if (aStops[i - 1].mPosition < 1 && aStops[i].mPosition >= 1) {
+      // Add a point to position 1.
+      aStops[i] = InterpolateColorStop(aStops[i - 1], aStops[i],
+                                       /* aPosition = */ 1,
+                                       aStops[i - 1].mColor);
+      // Remove all the elements whose position is greater than 1.
+      aStops.RemoveElementsAt(i + 1, aStops.Length() - (i + 1));
+    }
+    if (aStops[i - 1].mPosition <= 0 && aStops[i].mPosition > 0) {
+      // Add a point to position 0.
+      aStops[i - 1] = InterpolateColorStop(aStops[i - 1], aStops[i],
+                                           /* aPosition = */ 0,
+                                           aStops[i].mColor);
+      // Remove all of the preceding stops -- they are all negative.
+      aStops.RemoveElementsAt(0, i - 1);
+      break;
+    }
+  }
+
+  MOZ_ASSERT(aStops[0].mPosition >= -1e6);
+  MOZ_ASSERT(aStops.LastElement().mPosition - 1 <= 1e6);
+
+  // The end points won't exist yet if they don't fall in the original range of
+  // |aStops|. Create them if needed.
+  if (aStops[0].mPosition > 0) {
+    aStops.InsertElementAt(0, ColorStop(0, false, aStops[0].mColor));
+  }
+  if (aStops.LastElement().mPosition < 1) {
+    aStops.AppendElement(ColorStop(1, false, aStops.LastElement().mColor));
+  }
+}
+
+void
+nsCSSRendering::PaintGradient(nsPresContext* aPresContext,
+                              nsRenderingContext& aRenderingContext,
+                              nsStyleGradient* aGradient,
+                              const nsRect& aDirtyRect,
+                              const nsRect& aDest,
+                              const nsRect& aFillArea,
+                              const nsSize& aRepeatSize,
+                              const CSSIntRect& aSrc,
+                              const nsSize& aIntrinsicSize)
+{
+  PROFILER_LABEL("nsCSSRendering", "PaintGradient",
+    js::ProfileEntry::Category::GRAPHICS);
+
+  Telemetry::AutoTimer<Telemetry::GRADIENT_DURATION, Telemetry::Microsecond> gradientTimer;
+  if (aDest.IsEmpty() || aFillArea.IsEmpty()) {
+    return;
+  }
+
+  gfxContext *ctx = aRenderingContext.ThebesContext();
+  nscoord appUnitsPerDevPixel = aPresContext->AppUnitsPerDevPixel();
+  gfxSize srcSize = gfxSize(gfxFloat(aIntrinsicSize.width)/appUnitsPerDevPixel,
+                            gfxFloat(aIntrinsicSize.height)/appUnitsPerDevPixel);
+
+  bool cellContainsFill = aDest.Contains(aFillArea);
+
+  // Compute "gradient line" start and end relative to the intrinsic size of
+  // the gradient.
+  gfxPoint lineStart, lineEnd;
+  double radiusX = 0, radiusY = 0; // for radial gradients only
+  if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR) {
+    ComputeLinearGradientLine(aPresContext, aGradient, srcSize,
+                              &lineStart, &lineEnd);
+  } else {
+    ComputeRadialGradientLine(aPresContext, aGradient, srcSize,
+                              &lineStart, &lineEnd, &radiusX, &radiusY);
+  }
+  // Avoid sending Infs or Nans to downwind draw targets.
+  if (!lineStart.IsFinite() || !lineEnd.IsFinite()) {
+    lineStart = lineEnd = gfxPoint(0, 0);
+  }
+  gfxFloat lineLength = NS_hypot(lineEnd.x - lineStart.x,
+                                  lineEnd.y - lineStart.y);
+
+  MOZ_ASSERT(aGradient->mStops.Length() >= 2,
+             "The parser should reject gradients with less than two stops");
+
+  // Build color stop array and compute stop positions
+  nsTArray<ColorStop> stops;
+  // If there is a run of stops before stop i that did not have specified
+  // positions, then this is the index of the first stop in that run, otherwise
+  // it's -1.
+  int32_t firstUnsetPosition = -1;
+  for (uint32_t i = 0; i < aGradient->mStops.Length(); ++i) {
+    const nsStyleGradientStop& stop = aGradient->mStops[i];
+    double position;
+    switch (stop.mLocation.GetUnit()) {
+    case eStyleUnit_None:
+      if (i == 0) {
+        // First stop defaults to position 0.0
+        position = 0.0;
+      } else if (i == aGradient->mStops.Length() - 1) {
+        // Last stop defaults to position 1.0
+        position = 1.0;
+      } else {
+        // Other stops with no specified position get their position assigned
+        // later by interpolation, see below.
+        // Remeber where the run of stops with no specified position starts,
+        // if it starts here.
+        if (firstUnsetPosition < 0) {
+          firstUnsetPosition = i;
+        }
+        stops.AppendElement(ColorStop(0, stop.mIsInterpolationHint,
+                                      Color::FromABGR(stop.mColor)));
+        continue;
+      }
+      break;
+    case eStyleUnit_Percent:
+      position = stop.mLocation.GetPercentValue();
+      break;
+    case eStyleUnit_Coord:
+      position = lineLength < 1e-6 ? 0.0 :
+          stop.mLocation.GetCoordValue() / appUnitsPerDevPixel / lineLength;
+      break;
+    case eStyleUnit_Calc:
+      nsStyleCoord::Calc *calc;
+      calc = stop.mLocation.GetCalcValue();
+      position = calc->mPercent +
+          ((lineLength < 1e-6) ? 0.0 :
+          (NSAppUnitsToFloatPixels(calc->mLength, appUnitsPerDevPixel) / lineLength));
+      break;
+    default:
+      MOZ_ASSERT(false, "Unknown stop position type");
+    }
+
+    if (i > 0) {
+      // Prevent decreasing stop positions by advancing this position
+      // to the previous stop position, if necessary
+      position = std::max(position, stops[i - 1].mPosition);
+    }
+    stops.AppendElement(ColorStop(position, stop.mIsInterpolationHint,
+                                  Color::FromABGR(stop.mColor)));
+    if (firstUnsetPosition > 0) {
+      // Interpolate positions for all stops that didn't have a specified position
+      double p = stops[firstUnsetPosition - 1].mPosition;
+      double d = (stops[i].mPosition - p)/(i - firstUnsetPosition + 1);
+      for (uint32_t j = firstUnsetPosition; j < i; ++j) {
+        p += d;
+        stops[j].mPosition = p;
+      }
+      firstUnsetPosition = -1;
+    }
+  }
+
+  // If a non-repeating linear gradient is axis-aligned and there are no gaps
+  // between tiles, we can optimise away most of the work by converting to a
+  // repeating linear gradient and filling the whole destination rect at once.
+  bool forceRepeatToCoverTiles =
+    aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR &&
+    (lineStart.x == lineEnd.x) != (lineStart.y == lineEnd.y) &&
+    aRepeatSize.width == aDest.width && aRepeatSize.height == aDest.height &&
+    !aGradient->mRepeating && !aSrc.IsEmpty() && !cellContainsFill;
+
+  gfxMatrix matrix;
+  if (forceRepeatToCoverTiles) {
+    // Length of the source rectangle along the gradient axis.
+    double rectLen;
+    // The position of the start of the rectangle along the gradient.
+    double offset;
+
+    // The gradient line is "backwards". Flip the line upside down to make
+    // things easier, and then rotate the matrix to turn everything back the
+    // right way up.
+    if (lineStart.x > lineEnd.x || lineStart.y > lineEnd.y) {
+      std::swap(lineStart, lineEnd);
+      matrix.Scale(-1, -1);
+    }
+
+    // Fit the gradient line exactly into the source rect.
+    // aSrc is relative to aIntrinsincSize.
+    // srcRectDev will be relative to srcSize, so in the same coordinate space
+    // as lineStart / lineEnd.
+    gfxRect srcRectDev = nsLayoutUtils::RectToGfxRect(
+      CSSPixel::ToAppUnits(aSrc), appUnitsPerDevPixel);
+    if (lineStart.x != lineEnd.x) {
+      rectLen = srcRectDev.width;
+      offset = (srcRectDev.x - lineStart.x) / lineLength;
+      lineStart.x = srcRectDev.x;
+      lineEnd.x = srcRectDev.XMost();
+    } else {
+      rectLen = srcRectDev.height;
+      offset = (srcRectDev.y - lineStart.y) / lineLength;
+      lineStart.y = srcRectDev.y;
+      lineEnd.y = srcRectDev.YMost();
+    }
+
+    // Adjust gradient stop positions for the new gradient line.
+    double scale = lineLength / rectLen;
+    for (size_t i = 0; i < stops.Length(); i++) {
+      stops[i].mPosition = (stops[i].mPosition - offset) * fabs(scale);
+    }
+
+    // Clamp or extrapolate gradient stops to exactly [0, 1].
+    ClampColorStops(stops);
+
+    lineLength = rectLen;
+  }
+
+  // Eliminate negative-position stops if the gradient is radial.
+  double firstStop = stops[0].mPosition;
+  if (aGradient->mShape != NS_STYLE_GRADIENT_SHAPE_LINEAR && firstStop < 0.0) {
+    if (aGradient->mRepeating) {
+      // Choose an instance of the repeated pattern that gives us all positive
+      // stop-offsets.
+      double lastStop = stops[stops.Length() - 1].mPosition;
+      double stopDelta = lastStop - firstStop;
+      // If all the stops are in approximately the same place then logic below
+      // will kick in that makes us draw just the last stop color, so don't
+      // try to do anything in that case. We certainly need to avoid
+      // dividing by zero.
+      if (stopDelta >= 1e-6) {
+        double instanceCount = ceil(-firstStop/stopDelta);
+        // Advance stops by instanceCount multiples of the period of the
+        // repeating gradient.
+        double offset = instanceCount*stopDelta;
+        for (uint32_t i = 0; i < stops.Length(); i++) {
+          stops[i].mPosition += offset;
+        }
+      }
+    } else {
+      // Move negative-position stops to position 0.0. We may also need
+      // to set the color of the stop to the color the gradient should have
+      // at the center of the ellipse.
+      for (uint32_t i = 0; i < stops.Length(); i++) {
+        double pos = stops[i].mPosition;
+        if (pos < 0.0) {
+          stops[i].mPosition = 0.0;
+          // If this is the last stop, we don't need to adjust the color,
+          // it will fill the entire area.
+          if (i < stops.Length() - 1) {
+            double nextPos = stops[i + 1].mPosition;
+            // If nextPos is approximately equal to pos, then we don't
+            // need to adjust the color of this stop because it's
+            // not going to be displayed.
+            // If nextPos is negative, we don't need to adjust the color of
+            // this stop since it's not going to be displayed because
+            // nextPos will also be moved to 0.0.
+            if (nextPos >= 0.0 && nextPos - pos >= 1e-6) {
+              // Compute how far the new position 0.0 is along the interval
+              // between pos and nextPos.
+              // XXX Color interpolation (in cairo, too) should use the
+              // CSS 'color-interpolation' property!
+              float frac = float((0.0 - pos)/(nextPos - pos));
+              stops[i].mColor =
+                InterpolateColor(stops[i].mColor, stops[i + 1].mColor, frac);
+            }
+          }
+        }
+      }
+    }
+    firstStop = stops[0].mPosition;
+    MOZ_ASSERT(firstStop >= 0.0, "Failed to fix stop offsets");
+  }
+
+  if (aGradient->mShape != NS_STYLE_GRADIENT_SHAPE_LINEAR && !aGradient->mRepeating) {
+    // Direct2D can only handle a particular class of radial gradients because
+    // of the way the it specifies gradients. Setting firstStop to 0, when we
+    // can, will help us stay on the fast path. Currently we don't do this
+    // for repeating gradients but we could by adjusting the stop collection
+    // to start at 0
+    firstStop = 0;
+  }
+
+  double lastStop = stops[stops.Length() - 1].mPosition;
+  // Cairo gradients must have stop positions in the range [0, 1]. So,
+  // stop positions will be normalized below by subtracting firstStop and then
+  // multiplying by stopScale.
+  double stopScale;
+  double stopOrigin = firstStop;
+  double stopEnd = lastStop;
+  double stopDelta = lastStop - firstStop;
+  bool zeroRadius = aGradient->mShape != NS_STYLE_GRADIENT_SHAPE_LINEAR &&
+                      (radiusX < 1e-6 || radiusY < 1e-6);
+  if (stopDelta < 1e-6 || lineLength < 1e-6 || zeroRadius) {
+    // Stops are all at the same place. Map all stops to 0.0.
+    // For repeating radial gradients, or for any radial gradients with
+    // a zero radius, we need to fill with the last stop color, so just set
+    // both radii to 0.
+    if (aGradient->mRepeating || zeroRadius) {
+      radiusX = radiusY = 0.0;
+    }
+    stopDelta = 0.0;
+    lastStop = firstStop;
+  }
+
+  // Don't normalize non-repeating or degenerate gradients below 0..1
+  // This keeps the gradient line as large as the box and doesn't
+  // lets us avoiding having to get padding correct for stops
+  // at 0 and 1
+  if (!aGradient->mRepeating || stopDelta == 0.0) {
+    stopOrigin = std::min(stopOrigin, 0.0);
+    stopEnd = std::max(stopEnd, 1.0);
+  }
+  stopScale = 1.0/(stopEnd - stopOrigin);
+
+  // Create the gradient pattern.
+  RefPtr<gfxPattern> gradientPattern;
+  gfxPoint gradientStart;
+  gfxPoint gradientEnd;
+  if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR) {
+    // Compute the actual gradient line ends we need to pass to cairo after
+    // stops have been normalized.
+    gradientStart = lineStart + (lineEnd - lineStart)*stopOrigin;
+    gradientEnd = lineStart + (lineEnd - lineStart)*stopEnd;
+    gfxPoint gradientStopStart = lineStart + (lineEnd - lineStart)*firstStop;
+    gfxPoint gradientStopEnd = lineStart + (lineEnd - lineStart)*lastStop;
+
+    if (stopDelta == 0.0) {
+      // Stops are all at the same place. For repeating gradients, this will
+      // just paint the last stop color. We don't need to do anything.
+      // For non-repeating gradients, this should render as two colors, one
+      // on each "side" of the gradient line segment, which is a point. All
+      // our stops will be at 0.0; we just need to set the direction vector
+      // correctly.
+      gradientEnd = gradientStart + (lineEnd - lineStart);
+      gradientStopEnd = gradientStopStart + (lineEnd - lineStart);
+    }
+
+    gradientPattern = new gfxPattern(gradientStart.x, gradientStart.y,
+                                      gradientEnd.x, gradientEnd.y);
+  } else {
+    NS_ASSERTION(firstStop >= 0.0,
+                  "Negative stops not allowed for radial gradients");
+
+    // To form an ellipse, we'll stretch a circle vertically, if necessary.
+    // So our radii are based on radiusX.
+    double innerRadius = radiusX*stopOrigin;
+    double outerRadius = radiusX*stopEnd;
+    if (stopDelta == 0.0) {
+      // Stops are all at the same place.  See above (except we now have
+      // the inside vs. outside of an ellipse).
+      outerRadius = innerRadius + 1;
+    }
+    gradientPattern = new gfxPattern(lineStart.x, lineStart.y, innerRadius,
+                                     lineStart.x, lineStart.y, outerRadius);
+    if (radiusX != radiusY) {
+      // Stretch the circles into ellipses vertically by setting a transform
+      // in the pattern.
+      // Recall that this is the transform from user space to pattern space.
+      // So to stretch the ellipse by factor of P vertically, we scale
+      // user coordinates by 1/P.
+      matrix.Translate(lineStart);
+      matrix.Scale(1.0, radiusX/radiusY);
+      matrix.Translate(-lineStart);
+    }
+  }
+  // Use a pattern transform to take account of source and dest rects
+  matrix.Translate(gfxPoint(aPresContext->CSSPixelsToDevPixels(aSrc.x),
+                            aPresContext->CSSPixelsToDevPixels(aSrc.y)));
+  matrix.Scale(gfxFloat(aPresContext->CSSPixelsToAppUnits(aSrc.width))/aDest.width,
+               gfxFloat(aPresContext->CSSPixelsToAppUnits(aSrc.height))/aDest.height);
+  gradientPattern->SetMatrix(matrix);
+
+  if (gradientPattern->CairoStatus())
+    return;
+
+  if (stopDelta == 0.0) {
+    // Non-repeating gradient with all stops in same place -> just add
+    // first stop and last stop, both at position 0.
+    // Repeating gradient with all stops in the same place, or radial
+    // gradient with radius of 0 -> just paint the last stop color.
+    // We use firstStop offset to keep |stops| with same units (will later normalize to 0).
+    Color firstColor(stops[0].mColor);
+    Color lastColor(stops.LastElement().mColor);
+    stops.Clear();
+
+    if (!aGradient->mRepeating && !zeroRadius) {
+      stops.AppendElement(ColorStop(firstStop, false, firstColor));
+    }
+    stops.AppendElement(ColorStop(firstStop, false, lastColor));
+  }
+
+  ResolveMidpoints(stops);
+  ResolvePremultipliedAlpha(stops);
+
+  bool isRepeat = aGradient->mRepeating || forceRepeatToCoverTiles;
+
+  // Now set normalized color stops in pattern.
+  // Offscreen gradient surface cache (not a tile):
+  // On some backends (e.g. D2D), the GradientStops object holds an offscreen surface
+  // which is a lookup table used to evaluate the gradient. This surface can use
+  // much memory (ram and/or GPU ram) and can be expensive to create. So we cache it.
+  // The cache key correlates 1:1 with the arguments for CreateGradientStops (also the implied backend type)
+  // Note that GradientStop is a simple struct with a stop value (while GradientStops has the surface).
+  nsTArray<gfx::GradientStop> rawStops(stops.Length());
+  rawStops.SetLength(stops.Length());
+  for(uint32_t i = 0; i < stops.Length(); i++) {
+    rawStops[i].color = stops[i].mColor;
+    rawStops[i].offset = stopScale * (stops[i].mPosition - stopOrigin);
+  }
+  RefPtr<mozilla::gfx::GradientStops> gs =
+    gfxGradientCache::GetOrCreateGradientStops(ctx->GetDrawTarget(),
+                                               rawStops,
+                                               isRepeat ? gfx::ExtendMode::REPEAT : gfx::ExtendMode::CLAMP);
+  gradientPattern->SetColorStops(gs);
+
+  // Paint gradient tiles. This isn't terribly efficient, but doing it this
+  // way is simple and sure to get pixel-snapping right. We could speed things
+  // up by drawing tiles into temporary surfaces and copying those to the
+  // destination, but after pixel-snapping tiles may not all be the same size.
+  nsRect dirty;
+  if (!dirty.IntersectRect(aDirtyRect, aFillArea))
+    return;
+
+  gfxRect areaToFill =
+    nsLayoutUtils::RectToGfxRect(aFillArea, appUnitsPerDevPixel);
+  gfxRect dirtyAreaToFill = nsLayoutUtils::RectToGfxRect(dirty, appUnitsPerDevPixel);
+  dirtyAreaToFill.RoundOut();
+
+  gfxMatrix ctm = ctx->CurrentMatrix();
+  bool isCTMPreservingAxisAlignedRectangles = ctm.PreservesAxisAlignedRectangles();
+
+  // xStart/yStart are the top-left corner of the top-left tile.
+  nscoord xStart = FindTileStart(dirty.x, aDest.x, aRepeatSize.width);
+  nscoord yStart = FindTileStart(dirty.y, aDest.y, aRepeatSize.height);
+  nscoord xEnd = forceRepeatToCoverTiles ? xStart + aDest.width : dirty.XMost();
+  nscoord yEnd = forceRepeatToCoverTiles ? yStart + aDest.height : dirty.YMost();
+
+  // x and y are the top-left corner of the tile to draw
+  for (nscoord y = yStart; y < yEnd; y += aRepeatSize.height) {
+    for (nscoord x = xStart; x < xEnd; x += aRepeatSize.width) {
+      // The coordinates of the tile
+      gfxRect tileRect = nsLayoutUtils::RectToGfxRect(
+                      nsRect(x, y, aDest.width, aDest.height),
+                      appUnitsPerDevPixel);
+      // The actual area to fill with this tile is the intersection of this
+      // tile with the overall area we're supposed to be filling
+      gfxRect fillRect =
+        forceRepeatToCoverTiles ? areaToFill : tileRect.Intersect(areaToFill);
+      // Try snapping the fill rect. Snap its top-left and bottom-right
+      // independently to preserve the orientation.
+      gfxPoint snappedFillRectTopLeft = fillRect.TopLeft();
+      gfxPoint snappedFillRectTopRight = fillRect.TopRight();
+      gfxPoint snappedFillRectBottomRight = fillRect.BottomRight();
+      // Snap three points instead of just two to ensure we choose the
+      // correct orientation if there's a reflection.
+      if (isCTMPreservingAxisAlignedRectangles &&
+          ctx->UserToDevicePixelSnapped(snappedFillRectTopLeft, true) &&
+          ctx->UserToDevicePixelSnapped(snappedFillRectBottomRight, true) &&
+          ctx->UserToDevicePixelSnapped(snappedFillRectTopRight, true)) {
+        if (snappedFillRectTopLeft.x == snappedFillRectBottomRight.x ||
+            snappedFillRectTopLeft.y == snappedFillRectBottomRight.y) {
+          // Nothing to draw; avoid scaling by zero and other weirdness that
+          // could put the context in an error state.
+          continue;
+        }
+        // Set the context's transform to the transform that maps fillRect to
+        // snappedFillRect. The part of the gradient that was going to
+        // exactly fill fillRect will fill snappedFillRect instead.
+        gfxMatrix transform = gfxUtils::TransformRectToRect(fillRect,
+            snappedFillRectTopLeft, snappedFillRectTopRight,
+            snappedFillRectBottomRight);
+        ctx->SetMatrix(transform);
+      }
+      ctx->NewPath();
+      ctx->Rectangle(fillRect);
+
+      gfxRect dirtyFillRect = fillRect.Intersect(dirtyAreaToFill);
+      gfxRect fillRectRelativeToTile = dirtyFillRect - tileRect.TopLeft();
+      Color edgeColor;
+      if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR && !isRepeat &&
+          RectIsBeyondLinearGradientEdge(fillRectRelativeToTile, matrix, stops,
+                                         gradientStart, gradientEnd, &edgeColor)) {
+        ctx->SetColor(edgeColor);
+      } else {
+        ctx->SetMatrix(
+          ctx->CurrentMatrix().Copy().Translate(tileRect.TopLeft()));
+        ctx->SetPattern(gradientPattern);
+      }
+      ctx->Fill();
+      ctx->SetMatrix(ctm);
+    }
+  }
+}
+
+static CompositionOp
+DetermineCompositionOp(const nsCSSRendering::PaintBGParams& aParams,
+                       const nsStyleImageLayers& aLayers,
+                       uint32_t aLayerIndex)
+{
+  if (aParams.layer >= 0) {
+    // When drawing a single layer, use the specified composition op.
+    return aParams.compositionOp;
+  }
+
+  const nsStyleImageLayers::Layer& layer = aLayers.mLayers[aLayerIndex];
+  // When drawing all layers, get the compositon op from each image layer.
+  if (aParams.paintFlags & nsCSSRendering::PAINTBG_MASK_IMAGE) {
+    // Always using OP_OVER mode while drawing the bottom mask layer.
+    if (aLayerIndex == (aLayers.mImageCount - 1)) {
+      return CompositionOp::OP_OVER;
+    }
+
+    return nsCSSRendering::GetGFXCompositeMode(layer.mComposite);
+  }
+
+  return nsCSSRendering::GetGFXBlendMode(layer.mBlendMode);
+}
+
+DrawResult
+nsCSSRendering::PaintBackgroundWithSC(const PaintBGParams& aParams,
+                                      nsStyleContext *aBackgroundSC,
+                                      const nsStyleBorder& aBorder)
+{
+  NS_PRECONDITION(aParams.frame,
+                  "Frame is expected to be provided to PaintBackground");
+
+  // If we're drawing all layers, aCompositonOp is ignored, so make sure that
+  // it was left at its default value.
+  MOZ_ASSERT_IF(aParams.layer == -1,
+                aParams.compositionOp == CompositionOp::OP_OVER);
+
+  DrawResult result = DrawResult::SUCCESS;
+
+  // Check to see if we have an appearance defined.  If so, we let the theme
+  // renderer draw the background and bail out.
+  // XXXzw this ignores aParams.bgClipRect.
+  const nsStyleDisplay* displayData = aParams.frame->StyleDisplay();
+  if (displayData->mAppearance) {
+    nsITheme *theme = aParams.presCtx.GetTheme();
+    if (theme && theme->ThemeSupportsWidget(&aParams.presCtx,
+                                            aParams.frame,
+                                            displayData->mAppearance)) {
+      nsRect drawing(aParams.borderArea);
+      theme->GetWidgetOverflow(aParams.presCtx.DeviceContext(),
+                               aParams.frame, displayData->mAppearance,
+                               &drawing);
+      drawing.IntersectRect(drawing, aParams.dirtyRect);
+      theme->DrawWidgetBackground(&aParams.renderingCtx, aParams.frame,
+                                  displayData->mAppearance, aParams.borderArea,
+                                  drawing);
+      return DrawResult::SUCCESS;
+    }
+  }
+
+  // For canvas frames (in the CSS sense) we draw the background color using
+  // a solid color item that gets added in nsLayoutUtils::PaintFrame,
+  // or nsSubDocumentFrame::BuildDisplayList (bug 488242). (The solid
+  // color may be moved into nsDisplayCanvasBackground by
+  // nsPresShell::AddCanvasBackgroundColorItem, and painted by
+  // nsDisplayCanvasBackground directly.) Either way we don't need to
+  // paint the background color here.
+  bool isCanvasFrame = IsCanvasFrame(aParams.frame);
+
+  // Determine whether we are drawing background images and/or
+  // background colors.
+  bool drawBackgroundImage;
+  bool drawBackgroundColor;
+
+  nscolor bgColor = DetermineBackgroundColor(&aParams.presCtx,
+                                             aBackgroundSC,
+                                             aParams.frame,
+                                             drawBackgroundImage,
+                                             drawBackgroundColor);
+
+  bool paintMask = (aParams.paintFlags & PAINTBG_MASK_IMAGE);
+  const nsStyleImageLayers& layers = paintMask ?
+    aBackgroundSC->StyleSVGReset()->mMask :
+    aBackgroundSC->StyleBackground()->mImage;
+  // If we're drawing a specific layer, we don't want to draw the
+  // background color.
+  if ((drawBackgroundColor && aParams.layer >= 0) || paintMask) {
+    drawBackgroundColor = false;
+  }
+
+  // At this point, drawBackgroundImage and drawBackgroundColor are
+  // true if and only if we are actually supposed to paint an image or
+  // color into aDirtyRect, respectively.
+  if (!drawBackgroundImage && !drawBackgroundColor)
+    return DrawResult::SUCCESS;
+
+  // Compute the outermost boundary of the area that might be painted.
+  // Same coordinate space as aParams.borderArea & aParams.bgClipRect.
+  Sides skipSides = aParams.frame->GetSkipSides();
+  nsRect paintBorderArea =
+    ::BoxDecorationRectForBackground(aParams.frame, aParams.borderArea,
+                                     skipSides, &aBorder);
+  nsRect clipBorderArea =
+    ::BoxDecorationRectForBorder(aParams.frame, aParams.borderArea,
+                                 skipSides, &aBorder);
+
+  // The 'bgClipArea' (used only by the image tiling logic, far below)
+  // is the caller-provided aParams.bgClipRect if any, or else the area
+  // determined by the value of 'background-clip' in
+  // SetupCurrentBackgroundClip.  (Arguably it should be the
+  // intersection, but that breaks the table painter -- in particular,
+  // taking the intersection breaks reftests/bugs/403249-1[ab].)
+  gfxContext* ctx = aParams.renderingCtx.ThebesContext();
+  nscoord appUnitsPerPixel = aParams.presCtx.AppUnitsPerDevPixel();
+  ImageLayerClipState clipState;
+  if (aParams.bgClipRect) {
+    clipState.mBGClipArea = *aParams.bgClipRect;
+    clipState.mCustomClip = true;
+    clipState.mHasRoundedCorners = false;
+    SetupDirtyRects(clipState.mBGClipArea, aParams.dirtyRect, appUnitsPerPixel,
+                    &clipState.mDirtyRect, &clipState.mDirtyRectGfx);
+  } else {
+    GetImageLayerClip(layers.BottomLayer(),
+                      aParams.frame, aBorder, aParams.borderArea,
+                      aParams.dirtyRect,
+                      (aParams.paintFlags & PAINTBG_WILL_PAINT_BORDER),
+                      appUnitsPerPixel,
+                      &clipState);
+  }
+
+  // If we might be using a background color, go ahead and set it now.
+  if (drawBackgroundColor && !isCanvasFrame)
+    ctx->SetColor(Color::FromABGR(bgColor));
+
+  // NOTE: no Save() yet, we do that later by calling autoSR.EnsureSaved(ctx)
+  // in the cases we need it.
+  gfxContextAutoSaveRestore autoSR;
+
+  // If there is no background image, draw a color.  (If there is
+  // neither a background image nor a color, we wouldn't have gotten
+  // this far.)
+  if (!drawBackgroundImage) {
+    if (!isCanvasFrame) {
+      DrawBackgroundColor(clipState, ctx, appUnitsPerPixel);
+    }
+    return DrawResult::SUCCESS;
+  }
+
+  if (layers.mImageCount < 1) {
+    // Return if there are no background layers, all work from this point
+    // onwards happens iteratively on these.
+    return DrawResult::SUCCESS;
+  }
+
+  // Validate the layer range before we start iterating.
+  int32_t startLayer = aParams.layer;
+  int32_t nLayers = 1;
+  if (startLayer < 0) {
+    startLayer = (int32_t)layers.mImageCount - 1;
+    nLayers = layers.mImageCount;
+  }
+
+  // Ensure we get invalidated for loads of the image.  We need to do
+  // this here because this might be the only code that knows about the
+  // association of the style data with the frame.
+  if (aBackgroundSC != aParams.frame->StyleContext()) {
+    NS_FOR_VISIBLE_IMAGE_LAYERS_BACK_TO_FRONT_WITH_RANGE(i, layers, startLayer, nLayers) {
+      aParams.frame->AssociateImage(layers.mLayers[i].mImage,
+                                    &aParams.presCtx);
+    }
+  }
+
+  // The background color is rendered over the entire dirty area,
+  // even if the image isn't.
+  if (drawBackgroundColor && !isCanvasFrame) {
+    DrawBackgroundColor(clipState, ctx, appUnitsPerPixel);
+  }
+
+  if (drawBackgroundImage) {
+    bool clipSet = false;
+    uint8_t currentBackgroundClip = NS_STYLE_IMAGELAYER_CLIP_BORDER;
+    NS_FOR_VISIBLE_IMAGE_LAYERS_BACK_TO_FRONT_WITH_RANGE(i, layers, layers.mImageCount - 1,
+                                                         nLayers + (layers.mImageCount -
+                                                         startLayer - 1)) {
+      const nsStyleImageLayers::Layer& layer = layers.mLayers[i];
+      if (!aParams.bgClipRect) {
+        if (currentBackgroundClip != layer.mClip || !clipSet) {
+          currentBackgroundClip = layer.mClip;
+          // If clipSet is false that means this is the bottom layer and we
+          // already called GetImageLayerClip above and it stored its results
+          // in clipState.
+          if (clipSet) {
+            autoSR.Restore(); // reset the previous one
+            GetImageLayerClip(layer, aParams.frame,
+                              aBorder, aParams.borderArea, aParams.dirtyRect,
+                              (aParams.paintFlags & PAINTBG_WILL_PAINT_BORDER),
+                              appUnitsPerPixel, &clipState);
+          }
+          SetupImageLayerClip(clipState, ctx, appUnitsPerPixel, &autoSR);
+          clipSet = true;
+          if (!clipBorderArea.IsEqualEdges(aParams.borderArea)) {
+            // We're drawing the background for the joined continuation boxes
+            // so we need to clip that to the slice that we want for this
+            // frame.
+            gfxRect clip =
+              nsLayoutUtils::RectToGfxRect(aParams.borderArea, appUnitsPerPixel);
+            autoSR.EnsureSaved(ctx);
+            ctx->NewPath();
+            ctx->SnappedRectangle(clip);
+            ctx->Clip();
+          }
+        }
+      }
+      if ((aParams.layer < 0 || i == (uint32_t)startLayer) &&
+          !clipState.mDirtyRectGfx.IsEmpty()) {
+        CompositionOp co = DetermineCompositionOp(aParams, layers, i);
+        nsBackgroundLayerState state =
+          PrepareImageLayer(&aParams.presCtx, aParams.frame,
+                            aParams.paintFlags, paintBorderArea, clipState.mBGClipArea,
+                            layer, nullptr);
+        result &= state.mImageRenderer.PrepareResult();
+        if (!state.mFillArea.IsEmpty()) {
+          if (co != CompositionOp::OP_OVER) {
+            NS_ASSERTION(ctx->CurrentOp() == CompositionOp::OP_OVER,
+                         "It is assumed the initial op is OP_OVER, when it is "
+                         "restored later");
+            ctx->SetOp(co);
+          }
+
+          result &=
+            state.mImageRenderer.DrawBackground(&aParams.presCtx,
+                                                aParams.renderingCtx,
+                                                state.mDestArea, state.mFillArea,
+                                                state.mAnchor + paintBorderArea.TopLeft(),
+                                                clipState.mDirtyRect,
+                                                state.mRepeatSize);
+
+          if (co != CompositionOp::OP_OVER) {
+            ctx->SetOp(CompositionOp::OP_OVER);
+          }
+        }
+      }
+    }
+  }
+
+  return result;
+}
+
+nsRect
+nsCSSRendering::ComputeImageLayerPositioningArea(nsPresContext* aPresContext,
+                                                 nsIFrame* aForFrame,
+                                                 const nsRect& aBorderArea,
+                                                 const nsStyleImageLayers::Layer& aLayer,
+                                                 nsIFrame** aAttachedToFrame,
+                                                 bool* aOutIsTransformedFixed)
+{
+  // Compute background origin area relative to aBorderArea now as we may need
+  // it to compute the effective image size for a CSS gradient.
+  nsRect bgPositioningArea;
+
+  nsIAtom* frameType = aForFrame->GetType();
+  nsIFrame* geometryFrame = aForFrame;
+  if (MOZ_UNLIKELY(frameType == nsGkAtoms::scrollFrame &&
+                   NS_STYLE_IMAGELAYER_ATTACHMENT_LOCAL == aLayer.mAttachment)) {
+    nsIScrollableFrame* scrollableFrame = do_QueryFrame(aForFrame);
+    bgPositioningArea = nsRect(
+      scrollableFrame->GetScrolledFrame()->GetPosition()
+        // For the dir=rtl case:
+        + scrollableFrame->GetScrollRange().TopLeft(),
+      scrollableFrame->GetScrolledRect().Size());
+    // The ScrolledRect’s size does not include the borders or scrollbars,
+    // reverse the handling of background-origin
+    // compared to the common case below.
+    if (aLayer.mOrigin == NS_STYLE_IMAGELAYER_ORIGIN_BORDER) {
+      nsMargin border = geometryFrame->GetUsedBorder();
+      border.ApplySkipSides(geometryFrame->GetSkipSides());
+      bgPositioningArea.Inflate(border);
+      bgPositioningArea.Inflate(scrollableFrame->GetActualScrollbarSizes());
+    } else if (aLayer.mOrigin != NS_STYLE_IMAGELAYER_ORIGIN_PADDING) {
+      nsMargin padding = geometryFrame->GetUsedPadding();
+      padding.ApplySkipSides(geometryFrame->GetSkipSides());
+      bgPositioningArea.Deflate(padding);
+      NS_ASSERTION(aLayer.mOrigin == NS_STYLE_IMAGELAYER_ORIGIN_CONTENT,
+                   "unknown background-origin value");
+    }
+    *aAttachedToFrame = aForFrame;
+    return bgPositioningArea;
+  }
+
+  if (MOZ_UNLIKELY(frameType == nsGkAtoms::canvasFrame)) {
+    geometryFrame = aForFrame->PrincipalChildList().FirstChild();
+    // geometryFrame might be null if this canvas is a page created
+    // as an overflow container (e.g. the in-flow content has already
+    // finished and this page only displays the continuations of
+    // absolutely positioned content).
+    if (geometryFrame) {
+      bgPositioningArea = geometryFrame->GetRect();
+    }
+  } else {
+    bgPositioningArea = nsRect(nsPoint(0,0), aBorderArea.Size());
+  }
+
+  // Background images are tiled over the 'background-clip' area
+  // but the origin of the tiling is based on the 'background-origin' area
+  // XXX: Bug 1303623 will bring in new origin value, we should iterate from
+  // NS_STYLE_IMAGELAYER_ORIGIN_MARGIN instead of
+  // NS_STYLE_IMAGELAYER_ORIGIN_BORDER.
+  if (aLayer.mOrigin != NS_STYLE_IMAGELAYER_ORIGIN_BORDER && geometryFrame) {
+    nsMargin border = geometryFrame->GetUsedBorder();
+    if (aLayer.mOrigin != NS_STYLE_IMAGELAYER_ORIGIN_PADDING) {
+      border += geometryFrame->GetUsedPadding();
+      NS_ASSERTION(aLayer.mOrigin == NS_STYLE_IMAGELAYER_ORIGIN_CONTENT,
+                   "unknown background-origin value");
+    }
+    bgPositioningArea.Deflate(border);
+  }
+
+  nsIFrame* attachedToFrame = aForFrame;
+  if (NS_STYLE_IMAGELAYER_ATTACHMENT_FIXED == aLayer.mAttachment) {
+    // If it's a fixed background attachment, then the image is placed
+    // relative to the viewport, which is the area of the root frame
+    // in a screen context or the page content frame in a print context.
+    attachedToFrame = aPresContext->PresShell()->FrameManager()->GetRootFrame();
+    NS_ASSERTION(attachedToFrame, "no root frame");
+    nsIFrame* pageContentFrame = nullptr;
+    if (aPresContext->IsPaginated()) {
+      pageContentFrame =
+        nsLayoutUtils::GetClosestFrameOfType(aForFrame, nsGkAtoms::pageContentFrame);
+      if (pageContentFrame) {
+        attachedToFrame = pageContentFrame;
+      }
+      // else this is an embedded shell and its root frame is what we want
+    }
+
+    // If the background is affected by a transform, treat is as if it
+    // wasn't fixed.
+    if (nsLayoutUtils::IsTransformed(aForFrame, attachedToFrame)) {
+      attachedToFrame = aForFrame;
+      *aOutIsTransformedFixed = true;
+    } else {
+      // Set the background positioning area to the viewport's area
+      // (relative to aForFrame)
+      bgPositioningArea =
+        nsRect(-aForFrame->GetOffsetTo(attachedToFrame), attachedToFrame->GetSize());
+
+      if (!pageContentFrame) {
+        // Subtract the size of scrollbars.
+        nsIScrollableFrame* scrollableFrame =
+          aPresContext->PresShell()->GetRootScrollFrameAsScrollable();
+        if (scrollableFrame) {
+          nsMargin scrollbars = scrollableFrame->GetActualScrollbarSizes();
+          bgPositioningArea.Deflate(scrollbars);
+        }
+      }
+    }
+  }
+  *aAttachedToFrame = attachedToFrame;
+
+  return bgPositioningArea;
+}
+
+// Implementation of the formula for computation of background-repeat round
+// See http://dev.w3.org/csswg/css3-background/#the-background-size
+// This function returns the adjusted size of the background image.
+static nscoord
+ComputeRoundedSize(nscoord aCurrentSize, nscoord aPositioningSize)
+{
+  float repeatCount = NS_roundf(float(aPositioningSize) / float(aCurrentSize));
+  if (repeatCount < 1.0f) {
+    return aPositioningSize;
+  }
+  return nscoord(NS_lround(float(aPositioningSize) / repeatCount));
+}
+
+// Apply the CSS image sizing algorithm as it applies to background images.
+// See http://www.w3.org/TR/css3-background/#the-background-size .
+// aIntrinsicSize is the size that the background image 'would like to be'.
+// It can be found by calling nsImageRenderer::ComputeIntrinsicSize.
+static nsSize
+ComputeDrawnSizeForBackground(const CSSSizeOrRatio& aIntrinsicSize,
+                              const nsSize& aBgPositioningArea,
+                              const nsStyleImageLayers::Size& aLayerSize,
+                              uint8_t aXRepeat, uint8_t aYRepeat)
+{
+  nsSize imageSize;
+
+  // Size is dictated by cover or contain rules.
+  if (aLayerSize.mWidthType == nsStyleImageLayers::Size::eContain ||
+      aLayerSize.mWidthType == nsStyleImageLayers::Size::eCover) {
+    nsImageRenderer::FitType fitType =
+      aLayerSize.mWidthType == nsStyleImageLayers::Size::eCover
+        ? nsImageRenderer::COVER
+        : nsImageRenderer::CONTAIN;
+    imageSize = nsImageRenderer::ComputeConstrainedSize(aBgPositioningArea,
+                                                        aIntrinsicSize.mRatio,
+                                                        fitType);
+  } else {
+    // No cover/contain constraint, use default algorithm.
+    CSSSizeOrRatio specifiedSize;
+    if (aLayerSize.mWidthType == nsStyleImageLayers::Size::eLengthPercentage) {
+      specifiedSize.SetWidth(
+        aLayerSize.ResolveWidthLengthPercentage(aBgPositioningArea));
+    }
+    if (aLayerSize.mHeightType == nsStyleImageLayers::Size::eLengthPercentage) {
+      specifiedSize.SetHeight(
+        aLayerSize.ResolveHeightLengthPercentage(aBgPositioningArea));
+    }
+
+    imageSize = nsImageRenderer::ComputeConcreteSize(specifiedSize,
+                                                     aIntrinsicSize,
+                                                     aBgPositioningArea);
+  }
+
+  // See https://www.w3.org/TR/css3-background/#background-size .
+  // "If 'background-repeat' is 'round' for one (or both) dimensions, there is a second
+  //  step. The UA must scale the image in that dimension (or both dimensions) so that
+  //  it fits a whole number of times in the background positioning area."
+  // "If 'background-repeat' is 'round' for one dimension only and if 'background-size'
+  //  is 'auto' for the other dimension, then there is a third step: that other dimension
+  //  is scaled so that the original aspect ratio is restored."
+  bool isRepeatRoundInBothDimensions = aXRepeat == NS_STYLE_IMAGELAYER_REPEAT_ROUND &&
+                                       aYRepeat == NS_STYLE_IMAGELAYER_REPEAT_ROUND;
+
+  // Calculate the rounded size only if the background-size computation
+  // returned a correct size for the image.
+  if (imageSize.width && aXRepeat == NS_STYLE_IMAGELAYER_REPEAT_ROUND) {
+    imageSize.width = ComputeRoundedSize(imageSize.width, aBgPositioningArea.width);
+    if (!isRepeatRoundInBothDimensions &&
+        aLayerSize.mHeightType == nsStyleImageLayers::Size::DimensionType::eAuto) {
+      // Restore intrinsic rato
+      if (aIntrinsicSize.mRatio.width) {
+        float scale = float(aIntrinsicSize.mRatio.height) / aIntrinsicSize.mRatio.width;
+        imageSize.height = NSCoordSaturatingNonnegativeMultiply(imageSize.width, scale);
+      }
+    }
+  }
+
+  // Calculate the rounded size only if the background-size computation
+  // returned a correct size for the image.
+  if (imageSize.height && aYRepeat == NS_STYLE_IMAGELAYER_REPEAT_ROUND) {
+    imageSize.height = ComputeRoundedSize(imageSize.height, aBgPositioningArea.height);
+    if (!isRepeatRoundInBothDimensions &&
+        aLayerSize.mWidthType == nsStyleImageLayers::Size::DimensionType::eAuto) {
+      // Restore intrinsic rato
+      if (aIntrinsicSize.mRatio.height) {
+        float scale = float(aIntrinsicSize.mRatio.width) / aIntrinsicSize.mRatio.height;
+        imageSize.width = NSCoordSaturatingNonnegativeMultiply(imageSize.height, scale);
+      }
+    }
+  }
+
+  return imageSize;
+}
+
+/* ComputeSpacedRepeatSize
+ * aImageDimension: the image width/height
+ * aAvailableSpace: the background positioning area width/height
+ * aRepeat: determine whether the image is repeated
+ * Returns the image size plus gap size of app units for use as spacing
+ */
+static nscoord
+ComputeSpacedRepeatSize(nscoord aImageDimension,
+                        nscoord aAvailableSpace,
+                        bool& aRepeat) {
+  float ratio = static_cast<float>(aAvailableSpace) / aImageDimension;
+
+  if (ratio < 2.0f) { // If you can't repeat at least twice, then don't repeat.
+    aRepeat = false;
+    return aImageDimension;
+  } else {
+    aRepeat = true;
+    return (aAvailableSpace - aImageDimension) / (NSToIntFloor(ratio) - 1);
+  }
+}
+
+/* ComputeBorderSpacedRepeatSize
+ * aImageDimension: the image width/height
+ * aAvailableSpace: the background positioning area width/height
+ * aSpace: the space between each image
+ * Returns the image size plus gap size of app units for use as spacing
+ */
+static nscoord
+ComputeBorderSpacedRepeatSize(nscoord aImageDimension,
+                              nscoord aAvailableSpace,
+                              nscoord& aSpace)
+{
+  int32_t count = aAvailableSpace / aImageDimension;
+  aSpace = (aAvailableSpace - aImageDimension * count) / (count + 1);
+  return aSpace + aImageDimension;
+}
+
+nsBackgroundLayerState
+nsCSSRendering::PrepareImageLayer(nsPresContext* aPresContext,
+                                  nsIFrame* aForFrame,
+                                  uint32_t aFlags,
+                                  const nsRect& aBorderArea,
+                                  const nsRect& aBGClipRect,
+                                  const nsStyleImageLayers::Layer& aLayer,
+                                  bool* aOutIsTransformedFixed)
+{
+  /*
+   * The properties we need to keep in mind when drawing style image
+   * layers are:
+   *
+   *   background-image/ mask-image
+   *   background-repeat/ mask-repeat
+   *   background-attachment
+   *   background-position/ mask-position
+   *   background-clip/ mask-clip
+   *   background-origin/ mask-origin
+   *   background-size/ mask-size
+   *   background-blend-mode
+   *   box-decoration-break
+   *   mask-mode
+   *   mask-composite
+   *
+   * (background-color applies to the entire element and not to individual
+   * layers, so it is irrelevant to this method.)
+   *
+   * These properties have the following dependencies upon each other when
+   * determining rendering:
+   *
+   *   background-image/ mask-image
+   *     no dependencies
+   *   background-repeat/ mask-repeat
+   *     no dependencies
+   *   background-attachment
+   *     no dependencies
+   *   background-position/ mask-position
+   *     depends upon background-size/mask-size (for the image's scaled size)
+   *     and background-break (for the background positioning area)
+   *   background-clip/ mask-clip
+   *     no dependencies
+   *   background-origin/ mask-origin
+   *     depends upon background-attachment (only in the case where that value
+   *     is 'fixed')
+   *   background-size/ mask-size
+   *     depends upon box-decoration-break (for the background positioning area
+   *     for resolving percentages), background-image (for the image's intrinsic
+   *     size), background-repeat (if that value is 'round'), and
+   *     background-origin (for the background painting area, when
+   *     background-repeat is 'round')
+   *   background-blend-mode
+   *     no dependencies
+   *   mask-mode
+   *     no dependencies
+   *   mask-composite
+   *     no dependencies
+   *   box-decoration-break
+   *     no dependencies
+   *
+   * As a result of only-if dependencies we don't strictly do a topological
+   * sort of the above properties when processing, but it's pretty close to one:
+   *
+   *   background-clip/mask-clip (by caller)
+   *   background-image/ mask-image
+   *   box-decoration-break, background-origin/ mask origin
+   *   background-attachment (postfix for background-origin if 'fixed')
+   *   background-size/ mask-size
+   *   background-position/ mask-position
+   *   background-repeat/ mask-repeat
+   */
+
+  uint32_t irFlags = 0;
+  if (aFlags & nsCSSRendering::PAINTBG_SYNC_DECODE_IMAGES) {
+    irFlags |= nsImageRenderer::FLAG_SYNC_DECODE_IMAGES;
+  }
+  if (aFlags & nsCSSRendering::PAINTBG_TO_WINDOW) {
+    irFlags |= nsImageRenderer::FLAG_PAINTING_TO_WINDOW;
+  }
+
+  nsBackgroundLayerState state(aForFrame, &aLayer.mImage, irFlags);
+  if (!state.mImageRenderer.PrepareImage()) {
+    // There's no image or it's not ready to be painted.
+    if (aOutIsTransformedFixed) {
+      *aOutIsTransformedFixed = false;
+    }
+    return state;
+  }
+
+  // The frame to which the background is attached
+  nsIFrame* attachedToFrame = aForFrame;
+  // Is the background marked 'fixed', but affected by a transform?
+  bool transformedFixed = false;
+  // Compute background origin area relative to aBorderArea now as we may need
+  // it to compute the effective image size for a CSS gradient.
+  nsRect bgPositioningArea =
+    ComputeImageLayerPositioningArea(aPresContext, aForFrame, aBorderArea,
+                                     aLayer, &attachedToFrame, &transformedFixed);
+  if (aOutIsTransformedFixed) {
+    *aOutIsTransformedFixed = transformedFixed;
+  }
+
+  // For background-attachment:fixed backgrounds, we'll limit the area
+  // where the background can be drawn to the viewport.
+  nsRect bgClipRect = aBGClipRect;
+
+  // Compute the anchor point.
+  //
+  // relative to aBorderArea.TopLeft() (which is where the top-left
+  // of aForFrame's border-box will be rendered)
+  nsPoint imageTopLeft;
+  if (NS_STYLE_IMAGELAYER_ATTACHMENT_FIXED == aLayer.mAttachment && !transformedFixed) {
+    if (aFlags & nsCSSRendering::PAINTBG_TO_WINDOW) {
+      // Clip background-attachment:fixed backgrounds to the viewport, if we're
+      // painting to the screen and not transformed. This avoids triggering
+      // tiling in common cases, without affecting output since drawing is
+      // always clipped to the viewport when we draw to the screen. (But it's
+      // not a pure optimization since it can affect the values of pixels at the
+      // edge of the viewport --- whether they're sampled from a putative "next
+      // tile" or not.)
+      bgClipRect.IntersectRect(bgClipRect, bgPositioningArea + aBorderArea.TopLeft());
+    }
+  }
+
+  int repeatX = aLayer.mRepeat.mXRepeat;
+  int repeatY = aLayer.mRepeat.mYRepeat;
+
+  // Scale the image as specified for background-size and background-repeat.
+  // Also as required for proper background positioning when background-position
+  // is defined with percentages.
+  CSSSizeOrRatio intrinsicSize = state.mImageRenderer.ComputeIntrinsicSize();
+  nsSize bgPositionSize = bgPositioningArea.Size();
+  nsSize imageSize = ComputeDrawnSizeForBackground(intrinsicSize,
+                                                   bgPositionSize,
+                                                   aLayer.mSize,
+                                                   repeatX,
+                                                   repeatY);
+
+  if (imageSize.width <= 0 || imageSize.height <= 0)
+    return state;
+
+  state.mImageRenderer.SetPreferredSize(intrinsicSize,
+                                        imageSize);
+
+  // Compute the position of the background now that the background's size is
+  // determined.
+  nsImageRenderer::ComputeObjectAnchorPoint(aLayer.mPosition,
+                                            bgPositionSize, imageSize,
+                                            &imageTopLeft, &state.mAnchor);
+  state.mRepeatSize = imageSize;
+  if (repeatX == NS_STYLE_IMAGELAYER_REPEAT_SPACE) {
+    bool isRepeat;
+    state.mRepeatSize.width = ComputeSpacedRepeatSize(imageSize.width,
+                                                      bgPositionSize.width,
+                                                      isRepeat);
+    if (isRepeat) {
+      imageTopLeft.x = 0;
+      state.mAnchor.x = 0;
+    } else {
+      repeatX = NS_STYLE_IMAGELAYER_REPEAT_NO_REPEAT;
+    }
+  }
+
+  if (repeatY == NS_STYLE_IMAGELAYER_REPEAT_SPACE) {
+    bool isRepeat;
+    state.mRepeatSize.height = ComputeSpacedRepeatSize(imageSize.height,
+                                                       bgPositionSize.height,
+                                                       isRepeat);
+    if (isRepeat) {
+      imageTopLeft.y = 0;
+      state.mAnchor.y = 0;
+    } else {
+      repeatY = NS_STYLE_IMAGELAYER_REPEAT_NO_REPEAT;
+    }
+  }
+
+  imageTopLeft += bgPositioningArea.TopLeft();
+  state.mAnchor += bgPositioningArea.TopLeft();
+  state.mDestArea = nsRect(imageTopLeft + aBorderArea.TopLeft(), imageSize);
+  state.mFillArea = state.mDestArea;
+
+  ExtendMode repeatMode = ExtendMode::CLAMP;
+  if (repeatX == NS_STYLE_IMAGELAYER_REPEAT_REPEAT ||
+      repeatX == NS_STYLE_IMAGELAYER_REPEAT_ROUND ||
+      repeatX == NS_STYLE_IMAGELAYER_REPEAT_SPACE) {
+    state.mFillArea.x = bgClipRect.x;
+    state.mFillArea.width = bgClipRect.width;
+    repeatMode = ExtendMode::REPEAT_X;
+  }
+  if (repeatY == NS_STYLE_IMAGELAYER_REPEAT_REPEAT ||
+      repeatY == NS_STYLE_IMAGELAYER_REPEAT_ROUND ||
+      repeatY == NS_STYLE_IMAGELAYER_REPEAT_SPACE) {
+    state.mFillArea.y = bgClipRect.y;
+    state.mFillArea.height = bgClipRect.height;
+
+    /***
+     * We're repeating on the X axis already,
+     * so if we have to repeat in the Y axis,
+     * we really need to repeat in both directions.
+     */
+    if (repeatMode == ExtendMode::REPEAT_X) {
+      repeatMode = ExtendMode::REPEAT;
+    } else {
+      repeatMode = ExtendMode::REPEAT_Y;
+    }
+  }
+  state.mImageRenderer.SetExtendMode(repeatMode);
+  state.mImageRenderer.SetMaskOp(aLayer.mMaskMode);
+
+  state.mFillArea.IntersectRect(state.mFillArea, bgClipRect);
+
+  return state;
+}
+
+nsRect
+nsCSSRendering::GetBackgroundLayerRect(nsPresContext* aPresContext,
+                                       nsIFrame* aForFrame,
+                                       const nsRect& aBorderArea,
+                                       const nsRect& aClipRect,
+                                       const nsStyleImageLayers::Layer& aLayer,
+                                       uint32_t aFlags)
+{
+  Sides skipSides = aForFrame->GetSkipSides();
+  nsRect borderArea =
+    ::BoxDecorationRectForBackground(aForFrame, aBorderArea, skipSides);
+  nsBackgroundLayerState state =
+      PrepareImageLayer(aPresContext, aForFrame, aFlags, borderArea,
+                             aClipRect, aLayer);
+  return state.mFillArea;
+}
+
+static DrawResult
+DrawBorderImage(nsPresContext*       aPresContext,
+                nsRenderingContext&  aRenderingContext,
+                nsIFrame*            aForFrame,
+                const nsRect&        aBorderArea,
+                const nsStyleBorder& aStyleBorder,
+                const nsRect&        aDirtyRect,
+                Sides                aSkipSides,
+                PaintBorderFlags     aFlags)
+{
+  NS_PRECONDITION(aStyleBorder.IsBorderImageLoaded(),
+                  "drawing border image that isn't successfully loaded");
+
+  if (aDirtyRect.IsEmpty()) {
+    return DrawResult::SUCCESS;
+  }
+
+  uint32_t irFlags = 0;
+  if (aFlags & PaintBorderFlags::SYNC_DECODE_IMAGES) {
+    irFlags |= nsImageRenderer::FLAG_SYNC_DECODE_IMAGES;
+  }
+  nsImageRenderer renderer(aForFrame, &aStyleBorder.mBorderImageSource, irFlags);
+
+  // Ensure we get invalidated for loads and animations of the image.
+  // We need to do this here because this might be the only code that
+  // knows about the association of the style data with the frame.
+  // XXX We shouldn't really... since if anybody is passing in a
+  // different style, they'll potentially have the wrong size for the
+  // border too.
+  aForFrame->AssociateImage(aStyleBorder.mBorderImageSource, aPresContext);
+
+  if (!renderer.PrepareImage()) {
+    return renderer.PrepareResult();
+  }
+
+  // NOTE: no Save() yet, we do that later by calling autoSR.EnsureSaved()
+  // in case we need it.
+  gfxContextAutoSaveRestore autoSR;
+
+  // Determine the border image area, which by default corresponds to the
+  // border box but can be modified by 'border-image-outset'.
+  // Note that 'border-radius' do not apply to 'border-image' borders per
+  // <http://dev.w3.org/csswg/css-backgrounds/#corner-clipping>.
+  nsRect borderImgArea;
+  nsMargin borderWidths(aStyleBorder.GetComputedBorder());
+  nsMargin imageOutset(aStyleBorder.GetImageOutset());
+  if (::IsBoxDecorationSlice(aStyleBorder) && !aSkipSides.IsEmpty()) {
+    borderImgArea = ::BoxDecorationRectForBorder(aForFrame, aBorderArea,
+                                                 aSkipSides, &aStyleBorder);
+    if (borderImgArea.IsEqualEdges(aBorderArea)) {
+      // No need for a clip, just skip the sides we don't want.
+      borderWidths.ApplySkipSides(aSkipSides);
+      imageOutset.ApplySkipSides(aSkipSides);
+      borderImgArea.Inflate(imageOutset);
+    } else {
+      // We're drawing borders around the joined continuation boxes so we need
+      // to clip that to the slice that we want for this frame.
+      borderImgArea.Inflate(imageOutset);
+      imageOutset.ApplySkipSides(aSkipSides);
+      nsRect clip = aBorderArea;
+      clip.Inflate(imageOutset);
+      autoSR.EnsureSaved(aRenderingContext.ThebesContext());
+      aRenderingContext.ThebesContext()->
+        Clip(NSRectToSnappedRect(clip,
+                                 aForFrame->PresContext()->AppUnitsPerDevPixel(),
+                                 *aRenderingContext.GetDrawTarget()));
+    }
+  } else {
+    borderImgArea = aBorderArea;
+    borderImgArea.Inflate(imageOutset);
+  }
+
+  // Calculate the image size used to compute slice points.
+  CSSSizeOrRatio intrinsicSize = renderer.ComputeIntrinsicSize();
+  nsSize imageSize = nsImageRenderer::ComputeConcreteSize(CSSSizeOrRatio(),
+                                                          intrinsicSize,
+                                                          borderImgArea.Size());
+  renderer.SetPreferredSize(intrinsicSize, imageSize);
+
+  // Compute the used values of 'border-image-slice' and 'border-image-width';
+  // we do them together because the latter can depend on the former.
+  nsMargin slice;
+  nsMargin border;
+  NS_FOR_CSS_SIDES(s) {
+    nsStyleCoord coord = aStyleBorder.mBorderImageSlice.Get(s);
+    int32_t imgDimension = NS_SIDE_IS_VERTICAL(s)
+                           ? imageSize.width : imageSize.height;
+    nscoord borderDimension = NS_SIDE_IS_VERTICAL(s)
+                           ? borderImgArea.width : borderImgArea.height;
+    double value;
+    switch (coord.GetUnit()) {
+      case eStyleUnit_Percent:
+        value = coord.GetPercentValue() * imgDimension;
+        break;
+      case eStyleUnit_Factor:
+        value = nsPresContext::CSSPixelsToAppUnits(
+          NS_lround(coord.GetFactorValue()));
+        break;
+      default:
+        NS_NOTREACHED("unexpected CSS unit for image slice");
+        value = 0;
+        break;
+    }
+    if (value < 0)
+      value = 0;
+    if (value > imgDimension)
+      value = imgDimension;
+    slice.Side(s) = value;
+
+    coord = aStyleBorder.mBorderImageWidth.Get(s);
+    switch (coord.GetUnit()) {
+      case eStyleUnit_Coord: // absolute dimension
+        value = coord.GetCoordValue();
+        break;
+      case eStyleUnit_Percent:
+        value = coord.GetPercentValue() * borderDimension;
+        break;
+      case eStyleUnit_Factor:
+        value = coord.GetFactorValue() * borderWidths.Side(s);
+        break;
+      case eStyleUnit_Auto:  // same as the slice value, in CSS pixels
+        value = slice.Side(s);
+        break;
+      default:
+        NS_NOTREACHED("unexpected CSS unit for border image area division");
+        value = 0;
+        break;
+    }
+    // NSToCoordRoundWithClamp rounds towards infinity, but that's OK
+    // because we expect value to be non-negative.
+    MOZ_ASSERT(value >= 0);
+    border.Side(s) = NSToCoordRoundWithClamp(value);
+    MOZ_ASSERT(border.Side(s) >= 0);
+  }
+
+  // "If two opposite border-image-width offsets are large enough that they
+  // overlap, their used values are proportionately reduced until they no
+  // longer overlap."
+  uint32_t combinedBorderWidth = uint32_t(border.left) +
+                                 uint32_t(border.right);
+  double scaleX = combinedBorderWidth > uint32_t(borderImgArea.width)
+                  ? borderImgArea.width / double(combinedBorderWidth)
+                  : 1.0;
+  uint32_t combinedBorderHeight = uint32_t(border.top) +
+                                  uint32_t(border.bottom);
+  double scaleY = combinedBorderHeight > uint32_t(borderImgArea.height)
+                  ? borderImgArea.height / double(combinedBorderHeight)
+                  : 1.0;
+  double scale = std::min(scaleX, scaleY);
+  if (scale < 1.0) {
+    border.left *= scale;
+    border.right *= scale;
+    border.top *= scale;
+    border.bottom *= scale;
+    NS_ASSERTION(border.left + border.right <= borderImgArea.width &&
+                 border.top + border.bottom <= borderImgArea.height,
+                 "rounding error in width reduction???");
+  }
+
+  // These helper tables recharacterize the 'slice' and 'width' margins
+  // in a more convenient form: they are the x/y/width/height coords
+  // required for various bands of the border, and they have been transformed
+  // to be relative to the innerRect (for 'slice') or the page (for 'border').
+  enum {
+    LEFT, MIDDLE, RIGHT,
+    TOP = LEFT, BOTTOM = RIGHT
+  };
+  const nscoord borderX[3] = {
+    borderImgArea.x + 0,
+    borderImgArea.x + border.left,
+    borderImgArea.x + borderImgArea.width - border.right,
+  };
+  const nscoord borderY[3] = {
+    borderImgArea.y + 0,
+    borderImgArea.y + border.top,
+    borderImgArea.y + borderImgArea.height - border.bottom,
+  };
+  const nscoord borderWidth[3] = {
+    border.left,
+    borderImgArea.width - border.left - border.right,
+    border.right,
+  };
+  const nscoord borderHeight[3] = {
+    border.top,
+    borderImgArea.height - border.top - border.bottom,
+    border.bottom,
+  };
+  const int32_t sliceX[3] = {
+    0,
+    slice.left,
+    imageSize.width - slice.right,
+  };
+  const int32_t sliceY[3] = {
+    0,
+    slice.top,
+    imageSize.height - slice.bottom,
+  };
+  const int32_t sliceWidth[3] = {
+    slice.left,
+    std::max(imageSize.width - slice.left - slice.right, 0),
+    slice.right,
+  };
+  const int32_t sliceHeight[3] = {
+    slice.top,
+    std::max(imageSize.height - slice.top - slice.bottom, 0),
+    slice.bottom,
+  };
+
+  DrawResult result = DrawResult::SUCCESS;
+
+  // intrinsicSize.CanComputeConcreteSize() return false means we can not
+  // read intrinsic size from aStyleBorder.mBorderImageSource.
+  // In this condition, we pass imageSize(a resolved size comes from
+  // default sizing algorithm) to renderer as the viewport size.
+  Maybe<nsSize> svgViewportSize = intrinsicSize.CanComputeConcreteSize() ?
+    Nothing() : Some(imageSize);
+  bool hasIntrinsicRatio = intrinsicSize.HasRatio();
+  renderer.PurgeCacheForViewportChange(svgViewportSize, hasIntrinsicRatio);
+
+  for (int i = LEFT; i <= RIGHT; i++) {
+    for (int j = TOP; j <= BOTTOM; j++) {
+      uint8_t fillStyleH, fillStyleV;
+      nsSize unitSize;
+
+      if (i == MIDDLE && j == MIDDLE) {
+        // Discard the middle portion unless set to fill.
+        if (NS_STYLE_BORDER_IMAGE_SLICE_NOFILL ==
+            aStyleBorder.mBorderImageFill) {
+          continue;
+        }
+
+        NS_ASSERTION(NS_STYLE_BORDER_IMAGE_SLICE_FILL ==
+                     aStyleBorder.mBorderImageFill,
+                     "Unexpected border image fill");
+
+        // css-background:
+        //     The middle image's width is scaled by the same factor as the
+        //     top image unless that factor is zero or infinity, in which
+        //     case the scaling factor of the bottom is substituted, and
+        //     failing that, the width is not scaled. The height of the
+        //     middle image is scaled by the same factor as the left image
+        //     unless that factor is zero or infinity, in which case the
+        //     scaling factor of the right image is substituted, and failing
+        //     that, the height is not scaled.
+        gfxFloat hFactor, vFactor;
+
+        if (0 < border.left && 0 < slice.left)
+          vFactor = gfxFloat(border.left)/slice.left;
+        else if (0 < border.right && 0 < slice.right)
+          vFactor = gfxFloat(border.right)/slice.right;
+        else
+          vFactor = 1;
+
+        if (0 < border.top && 0 < slice.top)
+          hFactor = gfxFloat(border.top)/slice.top;
+        else if (0 < border.bottom && 0 < slice.bottom)
+          hFactor = gfxFloat(border.bottom)/slice.bottom;
+        else
+          hFactor = 1;
+
+        unitSize.width = sliceWidth[i]*hFactor;
+        unitSize.height = sliceHeight[j]*vFactor;
+        fillStyleH = aStyleBorder.mBorderImageRepeatH;
+        fillStyleV = aStyleBorder.mBorderImageRepeatV;
+
+      } else if (i == MIDDLE) { // top, bottom
+        // Sides are always stretched to the thickness of their border,
+        // and stretched proportionately on the other axis.
+        gfxFloat factor;
+        if (0 < borderHeight[j] && 0 < sliceHeight[j])
+          factor = gfxFloat(borderHeight[j])/sliceHeight[j];
+        else
+          factor = 1;
+
+        unitSize.width = sliceWidth[i]*factor;
+        unitSize.height = borderHeight[j];
+        fillStyleH = aStyleBorder.mBorderImageRepeatH;
+        fillStyleV = NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH;
+
+      } else if (j == MIDDLE) { // left, right
+        gfxFloat factor;
+        if (0 < borderWidth[i] && 0 < sliceWidth[i])
+          factor = gfxFloat(borderWidth[i])/sliceWidth[i];
+        else
+          factor = 1;
+
+        unitSize.width = borderWidth[i];
+        unitSize.height = sliceHeight[j]*factor;
+        fillStyleH = NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH;
+        fillStyleV = aStyleBorder.mBorderImageRepeatV;
+
+      } else {
+        // Corners are always stretched to fit the corner.
+        unitSize.width = borderWidth[i];
+        unitSize.height = borderHeight[j];
+        fillStyleH = NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH;
+        fillStyleV = NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH;
+      }
+
+      nsRect destArea(borderX[i], borderY[j], borderWidth[i], borderHeight[j]);
+      nsRect subArea(sliceX[i], sliceY[j], sliceWidth[i], sliceHeight[j]);
+      if (subArea.IsEmpty())
+        continue;
+
+      nsIntRect intSubArea = subArea.ToOutsidePixels(nsPresContext::AppUnitsPerCSSPixel());
+      result &=
+        renderer.DrawBorderImageComponent(aPresContext,
+                                          aRenderingContext, aDirtyRect,
+                                          destArea, CSSIntRect(intSubArea.x,
+                                                               intSubArea.y,
+                                                               intSubArea.width,
+                                                               intSubArea.height),
+                                          fillStyleH, fillStyleV,
+                                          unitSize, j * (RIGHT + 1) + i,
+                                          svgViewportSize, hasIntrinsicRatio);
+    }
+  }
+
+  return result;
+}
+
+// Begin table border-collapsing section
+// These functions were written to not disrupt the normal ones and yet satisfy some additional requirements
+// At some point, all functions should be unified to include the additional functionality that these provide
+
+static nscoord
+RoundIntToPixel(nscoord aValue,
+                nscoord aTwipsPerPixel,
+                bool    aRoundDown = false)
+{
+  if (aTwipsPerPixel <= 0)
+    // We must be rendering to a device that has a resolution greater than Twips!
+    // In that case, aValue is as accurate as it's going to get.
+    return aValue;
+
+  nscoord halfPixel = NSToCoordRound(aTwipsPerPixel / 2.0f);
+  nscoord extra = aValue % aTwipsPerPixel;
+  nscoord finalValue = (!aRoundDown && (extra >= halfPixel)) ? aValue + (aTwipsPerPixel - extra) : aValue - extra;
+  return finalValue;
+}
+
+static nscoord
+RoundFloatToPixel(float   aValue,
+                  nscoord aTwipsPerPixel,
+                  bool    aRoundDown = false)
+{
+  return RoundIntToPixel(NSToCoordRound(aValue), aTwipsPerPixel, aRoundDown);
+}
+
+static void SetPoly(const Rect& aRect, Point* poly)
+{
+  poly[0].x = aRect.x;
+  poly[0].y = aRect.y;
+  poly[1].x = aRect.x + aRect.width;
+  poly[1].y = aRect.y;
+  poly[2].x = aRect.x + aRect.width;
+  poly[2].y = aRect.y + aRect.height;
+  poly[3].x = aRect.x;
+  poly[3].y = aRect.y + aRect.height;
+}
+
+static void
+DrawDashedSegment(DrawTarget&          aDrawTarget,
+                  nsRect               aRect,
+                  nscoord              aDashLength,
+                  nscolor              aColor,
+                  int32_t              aAppUnitsPerDevPixel,
+                  nscoord              aTwipsPerPixel,
+                  bool                 aHorizontal)
+{
+  ColorPattern color(ToDeviceColor(aColor));
+  DrawOptions drawOptions(1.f, CompositionOp::OP_OVER, AntialiasMode::NONE);
+  StrokeOptions strokeOptions;
+
+  Float dash[2];
+  dash[0] = Float(aDashLength) / aAppUnitsPerDevPixel;
+  dash[1] = dash[0];
+
+  strokeOptions.mDashPattern = dash;
+  strokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dash);
+
+  if (aHorizontal) {
+    nsPoint left = (aRect.TopLeft() + aRect.BottomLeft()) / 2;
+    nsPoint right = (aRect.TopRight() + aRect.BottomRight()) / 2;
+    strokeOptions.mLineWidth = Float(aRect.height) / aAppUnitsPerDevPixel;
+    StrokeLineWithSnapping(left, right,
+                           aAppUnitsPerDevPixel, aDrawTarget,
+                           color, strokeOptions, drawOptions);
+  } else {
+    nsPoint top = (aRect.TopLeft() + aRect.TopRight()) / 2;
+    nsPoint bottom = (aRect.BottomLeft() + aRect.BottomRight()) / 2;
+    strokeOptions.mLineWidth = Float(aRect.width) / aAppUnitsPerDevPixel;
+    StrokeLineWithSnapping(top, bottom,
+                           aAppUnitsPerDevPixel, aDrawTarget,
+                           color, strokeOptions, drawOptions);
+  }
+}
+
+static void
+DrawSolidBorderSegment(DrawTarget&          aDrawTarget,
+                       nsRect               aRect,
+                       nscolor              aColor,
+                       int32_t              aAppUnitsPerDevPixel,
+                       nscoord              aTwipsPerPixel,
+                       uint8_t              aStartBevelSide = 0,
+                       nscoord              aStartBevelOffset = 0,
+                       uint8_t              aEndBevelSide = 0,
+                       nscoord              aEndBevelOffset = 0)
+{
+  ColorPattern color(ToDeviceColor(aColor));
+  DrawOptions drawOptions(1.f, CompositionOp::OP_OVER, AntialiasMode::NONE);
+
+  // We don't need to bevel single pixel borders
+  if ((aRect.width == aTwipsPerPixel) || (aRect.height == aTwipsPerPixel) ||
+      ((0 == aStartBevelOffset) && (0 == aEndBevelOffset))) {
+    // simple rectangle
+    aDrawTarget.FillRect(NSRectToSnappedRect(aRect, aAppUnitsPerDevPixel,
+                                             aDrawTarget),
+                         color, drawOptions);
+  }
+  else {
+    // polygon with beveling
+    Point poly[4];
+    SetPoly(NSRectToSnappedRect(aRect, aAppUnitsPerDevPixel, aDrawTarget),
+            poly);
+
+    Float startBevelOffset =
+      NSAppUnitsToFloatPixels(aStartBevelOffset, aAppUnitsPerDevPixel);
+    switch(aStartBevelSide) {
+    case NS_SIDE_TOP:
+      poly[0].x += startBevelOffset;
+      break;
+    case NS_SIDE_BOTTOM:
+      poly[3].x += startBevelOffset;
+      break;
+    case NS_SIDE_RIGHT:
+      poly[1].y += startBevelOffset;
+      break;
+    case NS_SIDE_LEFT:
+      poly[0].y += startBevelOffset;
+    }
+
+    Float endBevelOffset =
+      NSAppUnitsToFloatPixels(aEndBevelOffset, aAppUnitsPerDevPixel);
+    switch(aEndBevelSide) {
+    case NS_SIDE_TOP:
+      poly[1].x -= endBevelOffset;
+      break;
+    case NS_SIDE_BOTTOM:
+      poly[2].x -= endBevelOffset;
+      break;
+    case NS_SIDE_RIGHT:
+      poly[2].y -= endBevelOffset;
+      break;
+    case NS_SIDE_LEFT:
+      poly[3].y -= endBevelOffset;
+    }
+
+    RefPtr<PathBuilder> builder = aDrawTarget.CreatePathBuilder();
+    builder->MoveTo(poly[0]);
+    builder->LineTo(poly[1]);
+    builder->LineTo(poly[2]);
+    builder->LineTo(poly[3]);
+    builder->Close();
+    RefPtr<Path> path = builder->Finish();
+    aDrawTarget.Fill(path, color, drawOptions);
+  }
+}
+
+static void
+GetDashInfo(nscoord  aBorderLength,
+            nscoord  aDashLength,
+            nscoord  aTwipsPerPixel,
+            int32_t& aNumDashSpaces,
+            nscoord& aStartDashLength,
+            nscoord& aEndDashLength)
+{
+  aNumDashSpaces = 0;
+  if (aStartDashLength + aDashLength + aEndDashLength >= aBorderLength) {
+    aStartDashLength = aBorderLength;
+    aEndDashLength = 0;
+  }
+  else {
+    aNumDashSpaces = (aBorderLength - aDashLength)/ (2 * aDashLength); // round down
+    nscoord extra = aBorderLength - aStartDashLength - aEndDashLength - (((2 * aNumDashSpaces) - 1) * aDashLength);
+    if (extra > 0) {
+      nscoord half = RoundIntToPixel(extra / 2, aTwipsPerPixel);
+      aStartDashLength += half;
+      aEndDashLength += (extra - half);
+    }
+  }
+}
+
+void
+nsCSSRendering::DrawTableBorderSegment(DrawTarget&              aDrawTarget,
+                                       uint8_t                  aBorderStyle,
+                                       nscolor                  aBorderColor,
+                                       const nsStyleBackground* aBGColor,
+                                       const nsRect&            aBorder,
+                                       int32_t                  aAppUnitsPerDevPixel,
+                                       int32_t                  aAppUnitsPerCSSPixel,
+                                       uint8_t                  aStartBevelSide,
+                                       nscoord                  aStartBevelOffset,
+                                       uint8_t                  aEndBevelSide,
+                                       nscoord                  aEndBevelOffset)
+{
+  bool horizontal = ((NS_SIDE_TOP == aStartBevelSide) || (NS_SIDE_BOTTOM == aStartBevelSide));
+  nscoord twipsPerPixel = NSIntPixelsToAppUnits(1, aAppUnitsPerCSSPixel);
+  uint8_t ridgeGroove = NS_STYLE_BORDER_STYLE_RIDGE;
+
+  if ((twipsPerPixel >= aBorder.width) || (twipsPerPixel >= aBorder.height) ||
+      (NS_STYLE_BORDER_STYLE_DASHED == aBorderStyle) || (NS_STYLE_BORDER_STYLE_DOTTED == aBorderStyle)) {
+    // no beveling for 1 pixel border, dash or dot
+    aStartBevelOffset = 0;
+    aEndBevelOffset = 0;
+  }
+
+  switch (aBorderStyle) {
+  case NS_STYLE_BORDER_STYLE_NONE:
+  case NS_STYLE_BORDER_STYLE_HIDDEN:
+    //NS_ASSERTION(false, "style of none or hidden");
+    break;
+  case NS_STYLE_BORDER_STYLE_DOTTED:
+  case NS_STYLE_BORDER_STYLE_DASHED:
+    {
+      nscoord dashLength = (NS_STYLE_BORDER_STYLE_DASHED == aBorderStyle) ? DASH_LENGTH : DOT_LENGTH;
+      // make the dash length proportional to the border thickness
+      dashLength *= (horizontal) ? aBorder.height : aBorder.width;
+      // make the min dash length for the ends 1/2 the dash length
+      nscoord minDashLength = (NS_STYLE_BORDER_STYLE_DASHED == aBorderStyle)
+                              ? RoundFloatToPixel(((float)dashLength) / 2.0f, twipsPerPixel) : dashLength;
+      minDashLength = std::max(minDashLength, twipsPerPixel);
+      nscoord numDashSpaces = 0;
+      nscoord startDashLength = minDashLength;
+      nscoord endDashLength   = minDashLength;
+      if (horizontal) {
+        GetDashInfo(aBorder.width, dashLength, twipsPerPixel, numDashSpaces,
+                    startDashLength, endDashLength);
+        nsRect rect(aBorder.x, aBorder.y, startDashLength, aBorder.height);
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel);
+
+        rect.x += startDashLength + dashLength;
+        rect.width = aBorder.width
+                     - (startDashLength + endDashLength + dashLength);
+        DrawDashedSegment(aDrawTarget, rect, dashLength, aBorderColor,
+                          aAppUnitsPerDevPixel, twipsPerPixel, horizontal);
+
+        rect.x += rect.width;
+        rect.width = endDashLength;
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel);
+      }
+      else {
+        GetDashInfo(aBorder.height, dashLength, twipsPerPixel, numDashSpaces,
+                    startDashLength, endDashLength);
+        nsRect rect(aBorder.x, aBorder.y, aBorder.width, startDashLength);
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel);
+
+        rect.y += rect.height + dashLength;
+        rect.height = aBorder.height
+                      - (startDashLength + endDashLength + dashLength);
+        DrawDashedSegment(aDrawTarget, rect, dashLength, aBorderColor,
+                          aAppUnitsPerDevPixel, twipsPerPixel, horizontal);
+
+        rect.y += rect.height;
+        rect.height = endDashLength;
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel);
+      }
+    }
+    break;
+  case NS_STYLE_BORDER_STYLE_GROOVE:
+    ridgeGroove = NS_STYLE_BORDER_STYLE_GROOVE; // and fall through to ridge
+    MOZ_FALLTHROUGH;
+  case NS_STYLE_BORDER_STYLE_RIDGE:
+    if ((horizontal && (twipsPerPixel >= aBorder.height)) ||
+        (!horizontal && (twipsPerPixel >= aBorder.width))) {
+      // a one pixel border
+      DrawSolidBorderSegment(aDrawTarget, aBorder, aBorderColor,
+                             aAppUnitsPerDevPixel, twipsPerPixel,
+                             aStartBevelSide, aStartBevelOffset,
+                             aEndBevelSide, aEndBevelOffset);
+    }
+    else {
+      nscoord startBevel = (aStartBevelOffset > 0)
+                            ? RoundFloatToPixel(0.5f * (float)aStartBevelOffset, twipsPerPixel, true) : 0;
+      nscoord endBevel =   (aEndBevelOffset > 0)
+                            ? RoundFloatToPixel(0.5f * (float)aEndBevelOffset, twipsPerPixel, true) : 0;
+      mozilla::css::Side ridgeGrooveSide = (horizontal) ? NS_SIDE_TOP : NS_SIDE_LEFT;
+      // FIXME: In theory, this should use the visited-dependent
+      // background color, but I don't care.
+      nscolor bevelColor = MakeBevelColor(ridgeGrooveSide, ridgeGroove,
+                                          aBGColor->mBackgroundColor,
+                                          aBorderColor);
+      nsRect rect(aBorder);
+      nscoord half;
+      if (horizontal) { // top, bottom
+        half = RoundFloatToPixel(0.5f * (float)aBorder.height, twipsPerPixel);
+        rect.height = half;
+        if (NS_SIDE_TOP == aStartBevelSide) {
+          rect.x += startBevel;
+          rect.width -= startBevel;
+        }
+        if (NS_SIDE_TOP == aEndBevelSide) {
+          rect.width -= endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, rect, bevelColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+      }
+      else { // left, right
+        half = RoundFloatToPixel(0.5f * (float)aBorder.width, twipsPerPixel);
+        rect.width = half;
+        if (NS_SIDE_LEFT == aStartBevelSide) {
+          rect.y += startBevel;
+          rect.height -= startBevel;
+        }
+        if (NS_SIDE_LEFT == aEndBevelSide) {
+          rect.height -= endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, rect, bevelColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+      }
+
+      rect = aBorder;
+      ridgeGrooveSide = (NS_SIDE_TOP == ridgeGrooveSide) ? NS_SIDE_BOTTOM : NS_SIDE_RIGHT;
+      // FIXME: In theory, this should use the visited-dependent
+      // background color, but I don't care.
+      bevelColor = MakeBevelColor(ridgeGrooveSide, ridgeGroove,
+                                  aBGColor->mBackgroundColor, aBorderColor);
+      if (horizontal) {
+        rect.y = rect.y + half;
+        rect.height = aBorder.height - half;
+        if (NS_SIDE_BOTTOM == aStartBevelSide) {
+          rect.x += startBevel;
+          rect.width -= startBevel;
+        }
+        if (NS_SIDE_BOTTOM == aEndBevelSide) {
+          rect.width -= endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, rect, bevelColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+      }
+      else {
+        rect.x = rect.x + half;
+        rect.width = aBorder.width - half;
+        if (NS_SIDE_RIGHT == aStartBevelSide) {
+          rect.y += aStartBevelOffset - startBevel;
+          rect.height -= startBevel;
+        }
+        if (NS_SIDE_RIGHT == aEndBevelSide) {
+          rect.height -= endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, rect, bevelColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+      }
+    }
+    break;
+  case NS_STYLE_BORDER_STYLE_DOUBLE:
+    // We can only do "double" borders if the thickness of the border
+    // is more than 2px.  Otherwise, we fall through to painting a
+    // solid border.
+    if ((aBorder.width > 2*twipsPerPixel || horizontal) &&
+        (aBorder.height > 2*twipsPerPixel || !horizontal)) {
+      nscoord startBevel = (aStartBevelOffset > 0)
+                            ? RoundFloatToPixel(0.333333f * (float)aStartBevelOffset, twipsPerPixel) : 0;
+      nscoord endBevel =   (aEndBevelOffset > 0)
+                            ? RoundFloatToPixel(0.333333f * (float)aEndBevelOffset, twipsPerPixel) : 0;
+      if (horizontal) { // top, bottom
+        nscoord thirdHeight = RoundFloatToPixel(0.333333f * (float)aBorder.height, twipsPerPixel);
+
+        // draw the top line or rect
+        nsRect topRect(aBorder.x, aBorder.y, aBorder.width, thirdHeight);
+        if (NS_SIDE_TOP == aStartBevelSide) {
+          topRect.x += aStartBevelOffset - startBevel;
+          topRect.width -= aStartBevelOffset - startBevel;
+        }
+        if (NS_SIDE_TOP == aEndBevelSide) {
+          topRect.width -= aEndBevelOffset - endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, topRect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+
+        // draw the botom line or rect
+        nscoord heightOffset = aBorder.height - thirdHeight;
+        nsRect bottomRect(aBorder.x, aBorder.y + heightOffset, aBorder.width, aBorder.height - heightOffset);
+        if (NS_SIDE_BOTTOM == aStartBevelSide) {
+          bottomRect.x += aStartBevelOffset - startBevel;
+          bottomRect.width -= aStartBevelOffset - startBevel;
+        }
+        if (NS_SIDE_BOTTOM == aEndBevelSide) {
+          bottomRect.width -= aEndBevelOffset - endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, bottomRect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+      }
+      else { // left, right
+        nscoord thirdWidth = RoundFloatToPixel(0.333333f * (float)aBorder.width, twipsPerPixel);
+
+        nsRect leftRect(aBorder.x, aBorder.y, thirdWidth, aBorder.height);
+        if (NS_SIDE_LEFT == aStartBevelSide) {
+          leftRect.y += aStartBevelOffset - startBevel;
+          leftRect.height -= aStartBevelOffset - startBevel;
+        }
+        if (NS_SIDE_LEFT == aEndBevelSide) {
+          leftRect.height -= aEndBevelOffset - endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, leftRect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+
+        nscoord widthOffset = aBorder.width - thirdWidth;
+        nsRect rightRect(aBorder.x + widthOffset, aBorder.y, aBorder.width - widthOffset, aBorder.height);
+        if (NS_SIDE_RIGHT == aStartBevelSide) {
+          rightRect.y += aStartBevelOffset - startBevel;
+          rightRect.height -= aStartBevelOffset - startBevel;
+        }
+        if (NS_SIDE_RIGHT == aEndBevelSide) {
+          rightRect.height -= aEndBevelOffset - endBevel;
+        }
+        DrawSolidBorderSegment(aDrawTarget, rightRect, aBorderColor,
+                               aAppUnitsPerDevPixel, twipsPerPixel,
+                               aStartBevelSide, startBevel, aEndBevelSide,
+                               endBevel);
+      }
+      break;
+    }
+    // else fall through to solid
+    MOZ_FALLTHROUGH;
+  case NS_STYLE_BORDER_STYLE_SOLID:
+    DrawSolidBorderSegment(aDrawTarget, aBorder, aBorderColor,
+                           aAppUnitsPerDevPixel, twipsPerPixel, aStartBevelSide,
+                           aStartBevelOffset, aEndBevelSide, aEndBevelOffset);
+    break;
+  case NS_STYLE_BORDER_STYLE_OUTSET:
+  case NS_STYLE_BORDER_STYLE_INSET:
+    NS_ASSERTION(false, "inset, outset should have been converted to groove, ridge");
+    break;
+  case NS_STYLE_BORDER_STYLE_AUTO:
+    NS_ASSERTION(false, "Unexpected 'auto' table border");
+    break;
+  }
+}
+
+// End table border-collapsing section
+
+Rect
+nsCSSRendering::ExpandPaintingRectForDecorationLine(
+                  nsIFrame* aFrame,
+                  const uint8_t aStyle,
+                  const Rect& aClippedRect,
+                  const Float aICoordInFrame,
+                  const Float aCycleLength,
+                  bool aVertical)
+{
+  switch (aStyle) {
+    case NS_STYLE_TEXT_DECORATION_STYLE_DOTTED:
+    case NS_STYLE_TEXT_DECORATION_STYLE_DASHED:
+    case NS_STYLE_TEXT_DECORATION_STYLE_WAVY:
+      break;
+    default:
+      NS_ERROR("Invalid style was specified");
+      return aClippedRect;
+  }
+
+  nsBlockFrame* block = nullptr;
+  // Note that when we paint the decoration lines in relative positioned
+  // box, we should paint them like all of the boxes are positioned as static.
+  nscoord framePosInBlockAppUnits = 0;
+  for (nsIFrame* f = aFrame; f; f = f->GetParent()) {
+    block = do_QueryFrame(f);
+    if (block) {
+      break;
+    }
+    framePosInBlockAppUnits += aVertical ?
+      f->GetNormalPosition().y : f->GetNormalPosition().x;
+  }
+
+  NS_ENSURE_TRUE(block, aClippedRect);
+
+  nsPresContext *pc = aFrame->PresContext();
+  Float framePosInBlock = Float(pc->AppUnitsToGfxUnits(framePosInBlockAppUnits));
+  int32_t rectPosInBlock =
+    int32_t(NS_round(framePosInBlock + aICoordInFrame));
+  int32_t extraStartEdge =
+    rectPosInBlock - (rectPosInBlock / int32_t(aCycleLength) * aCycleLength);
+  Rect rect(aClippedRect);
+  if (aVertical) {
+    rect.y -= extraStartEdge;
+    rect.height += extraStartEdge;
+  } else {
+    rect.x -= extraStartEdge;
+    rect.width += extraStartEdge;
+  }
+  return rect;
+}
+
+void
+nsCSSRendering::PaintDecorationLine(nsIFrame* aFrame, DrawTarget& aDrawTarget,
+                                    const PaintDecorationLineParams& aParams)
+{
+  NS_ASSERTION(aParams.style != NS_STYLE_TEXT_DECORATION_STYLE_NONE,
+               "aStyle is none");
+
+  Rect rect = ToRect(GetTextDecorationRectInternal(aParams.pt, aParams));
+  if (rect.IsEmpty() || !rect.Intersects(aParams.dirtyRect)) {
+    return;
+  }
+
+  if (aParams.decoration != NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE &&
+      aParams.decoration != NS_STYLE_TEXT_DECORATION_LINE_OVERLINE &&
+      aParams.decoration != NS_STYLE_TEXT_DECORATION_LINE_LINE_THROUGH) {
+    NS_ERROR("Invalid decoration value!");
+    return;
+  }
+
+  Float lineThickness = std::max(NS_round(aParams.lineSize.height), 1.0);
+
+  ColorPattern color(ToDeviceColor(aParams.color));
+  StrokeOptions strokeOptions(lineThickness);
+  DrawOptions drawOptions;
+
+  Float dash[2];
+
+  AutoPopClips autoPopClips(&aDrawTarget);
+
+  switch (aParams.style) {
+    case NS_STYLE_TEXT_DECORATION_STYLE_SOLID:
+    case NS_STYLE_TEXT_DECORATION_STYLE_DOUBLE:
+      break;
+    case NS_STYLE_TEXT_DECORATION_STYLE_DASHED: {
+      autoPopClips.PushClipRect(rect);
+      Float dashWidth = lineThickness * DOT_LENGTH * DASH_LENGTH;
+      dash[0] = dashWidth;
+      dash[1] = dashWidth;
+      strokeOptions.mDashPattern = dash;
+      strokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dash);
+      strokeOptions.mLineCap = CapStyle::BUTT;
+      rect = ExpandPaintingRectForDecorationLine(aFrame, aParams.style,
+                                                 rect, aParams.icoordInFrame,
+                                                 dashWidth * 2,
+                                                 aParams.vertical);
+      // We should continue to draw the last dash even if it is not in the rect.
+      rect.width += dashWidth;
+      break;
+    }
+    case NS_STYLE_TEXT_DECORATION_STYLE_DOTTED: {
+      autoPopClips.PushClipRect(rect);
+      Float dashWidth = lineThickness * DOT_LENGTH;
+      if (lineThickness > 2.0) {
+        dash[0] = 0.f;
+        dash[1] = dashWidth * 2.f;
+        strokeOptions.mLineCap = CapStyle::ROUND;
+      } else {
+        dash[0] = dashWidth;
+        dash[1] = dashWidth;
+      }
+      strokeOptions.mDashPattern = dash;
+      strokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dash);
+      rect = ExpandPaintingRectForDecorationLine(aFrame, aParams.style,
+                                                 rect, aParams.icoordInFrame,
+                                                 dashWidth * 2,
+                                                 aParams.vertical);
+      // We should continue to draw the last dot even if it is not in the rect.
+      rect.width += dashWidth;
+      break;
+    }
+    case NS_STYLE_TEXT_DECORATION_STYLE_WAVY:
+      autoPopClips.PushClipRect(rect);
+      if (lineThickness > 2.0) {
+        drawOptions.mAntialiasMode = AntialiasMode::SUBPIXEL;
+      } else {
+        // Don't use anti-aliasing here.  Because looks like lighter color wavy
+        // line at this case.  And probably, users don't think the
+        // non-anti-aliased wavy line is not pretty.
+        drawOptions.mAntialiasMode = AntialiasMode::NONE;
+      }
+      break;
+    default:
+      NS_ERROR("Invalid style value!");
+      return;
+  }
+
+  // The block-direction position should be set to the middle of the line.
+  if (aParams.vertical) {
+    rect.x += lineThickness / 2;
+  } else {
+    rect.y += lineThickness / 2;
+  }
+
+  switch (aParams.style) {
+    case NS_STYLE_TEXT_DECORATION_STYLE_SOLID:
+    case NS_STYLE_TEXT_DECORATION_STYLE_DOTTED:
+    case NS_STYLE_TEXT_DECORATION_STYLE_DASHED: {
+      Point p1 = rect.TopLeft();
+      Point p2 = aParams.vertical ? rect.BottomLeft() : rect.TopRight();
+      aDrawTarget.StrokeLine(p1, p2, color, strokeOptions, drawOptions);
+      return;
+    }
+    case NS_STYLE_TEXT_DECORATION_STYLE_DOUBLE: {
+      /**
+       *  We are drawing double line as:
+       *
+       * +-------------------------------------------+
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+       * |                                           |
+       * |                                           |
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+       * +-------------------------------------------+
+       */
+      Point p1 = rect.TopLeft();
+      Point p2 = aParams.vertical ? rect.BottomLeft() : rect.TopRight();
+      aDrawTarget.StrokeLine(p1, p2, color, strokeOptions, drawOptions);
+
+      if (aParams.vertical) {
+        rect.width -= lineThickness;
+      } else {
+        rect.height -= lineThickness;
+      }
+
+      p1 = aParams.vertical ? rect.TopRight() : rect.BottomLeft();
+      p2 = rect.BottomRight();
+      aDrawTarget.StrokeLine(p1, p2, color, strokeOptions, drawOptions);
+      return;
+    }
+    case NS_STYLE_TEXT_DECORATION_STYLE_WAVY: {
+      /**
+       *  We are drawing wavy line as:
+       *
+       *  P: Path, X: Painted pixel
+       *
+       *     +---------------------------------------+
+       *   XX|X            XXXXXX            XXXXXX  |
+       *   PP|PX          XPPPPPPX          XPPPPPPX |    ^
+       *   XX|XPX        XPXXXXXXPX        XPXXXXXXPX|    |
+       *     | XPX      XPX      XPX      XPX      XP|X   |adv
+       *     |  XPXXXXXXPX        XPXXXXXXPX        X|PX  |
+       *     |   XPPPPPPX          XPPPPPPX          |XPX v
+       *     |    XXXXXX            XXXXXX           | XX
+       *     +---------------------------------------+
+       *      <---><--->                                ^
+       *      adv  flatLengthAtVertex                   rightMost
+       *
+       *  1. Always starts from top-left of the drawing area, however, we need
+       *     to draw  the line from outside of the rect.  Because the start
+       *     point of the line is not good style if we draw from inside it.
+       *  2. First, draw horizontal line from outside the rect to top-left of
+       *     the rect;
+       *  3. Goes down to bottom of the area at 45 degrees.
+       *  4. Slides to right horizontaly, see |flatLengthAtVertex|.
+       *  5. Goes up to top of the area at 45 degrees.
+       *  6. Slides to right horizontaly.
+       *  7. Repeat from 2 until reached to right-most edge of the area.
+       *
+       * In the vertical case, swap horizontal and vertical coordinates and
+       * directions in the above description.
+       */
+
+      Float& rectICoord = aParams.vertical ? rect.y : rect.x;
+      Float& rectISize = aParams.vertical ? rect.height : rect.width;
+      const Float rectBSize = aParams.vertical ? rect.width : rect.height;
+
+      const Float adv = rectBSize - lineThickness;
+      const Float flatLengthAtVertex =
+        std::max((lineThickness - 1.0) * 2.0, 1.0);
+
+      // Align the start of wavy lines to the nearest ancestor block.
+      const Float cycleLength = 2 * (adv + flatLengthAtVertex);
+      rect = ExpandPaintingRectForDecorationLine(aFrame, aParams.style, rect,
+                                                 aParams.icoordInFrame,
+                                                 cycleLength, aParams.vertical);
+      // figure out if we can trim whole cycles from the left and right edges
+      // of the line, to try and avoid creating an unnecessarily long and
+      // complex path
+      const Float dirtyRectICoord = aParams.vertical ? aParams.dirtyRect.y
+                                                     : aParams.dirtyRect.x;
+      int32_t skipCycles = floor((dirtyRectICoord - rectICoord) / cycleLength);
+      if (skipCycles > 0) {
+        rectICoord += skipCycles * cycleLength;
+        rectISize -= skipCycles * cycleLength;
+      }
+
+      rectICoord += lineThickness / 2.0;
+      Point pt(rect.TopLeft());
+      Float& ptICoord = aParams.vertical ? pt.y : pt.x;
+      Float& ptBCoord = aParams.vertical ? pt.x : pt.y;
+      if (aParams.vertical) {
+        ptBCoord += adv + lineThickness / 2.0;
+      }
+      Float iCoordLimit = ptICoord + rectISize + lineThickness;
+
+      const Float dirtyRectIMost = aParams.vertical ?
+        aParams.dirtyRect.YMost() : aParams.dirtyRect.XMost();
+      skipCycles = floor((iCoordLimit - dirtyRectIMost) / cycleLength);
+      if (skipCycles > 0) {
+        iCoordLimit -= skipCycles * cycleLength;
+      }
+
+      RefPtr<PathBuilder> builder = aDrawTarget.CreatePathBuilder();
+      RefPtr<Path> path;
+
+      ptICoord -= lineThickness;
+      builder->MoveTo(pt); // 1
+
+      ptICoord = rectICoord;
+      builder->LineTo(pt); // 2
+
+      // In vertical mode, to go "down" relative to the text we need to
+      // decrease the block coordinate, whereas in horizontal we increase
+      // it. So the sense of this flag is effectively inverted.
+      bool goDown = aParams.vertical ? false : true;
+      uint32_t iter = 0;
+      while (ptICoord < iCoordLimit) {
+        if (++iter > 1000) {
+          // stroke the current path and start again, to avoid pathological
+          // behavior in cairo with huge numbers of path segments
+          path = builder->Finish();
+          aDrawTarget.Stroke(path, color, strokeOptions, drawOptions);
+          builder = aDrawTarget.CreatePathBuilder();
+          builder->MoveTo(pt);
+          iter = 0;
+        }
+        ptICoord += adv;
+        ptBCoord += goDown ? adv : -adv;
+
+        builder->LineTo(pt); // 3 and 5
+
+        ptICoord += flatLengthAtVertex;
+        builder->LineTo(pt); // 4 and 6
+
+        goDown = !goDown;
+      }
+      path = builder->Finish();
+      aDrawTarget.Stroke(path, color, strokeOptions, drawOptions);
+      return;
+    }
+    default:
+      NS_ERROR("Invalid style value!");
+  }
+}
+
+Rect
+nsCSSRendering::DecorationLineToPath(const PaintDecorationLineParams& aParams)
+{
+  NS_ASSERTION(aParams.style != NS_STYLE_TEXT_DECORATION_STYLE_NONE,
+               "aStyle is none");
+
+  Rect path; // To benefit from RVO, we return this from all return points
+
+  Rect rect = ToRect(GetTextDecorationRectInternal(aParams.pt, aParams));
+  if (rect.IsEmpty() || !rect.Intersects(aParams.dirtyRect)) {
+    return path;
+  }
+
+  if (aParams.decoration != NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE &&
+      aParams.decoration != NS_STYLE_TEXT_DECORATION_LINE_OVERLINE &&
+      aParams.decoration != NS_STYLE_TEXT_DECORATION_LINE_LINE_THROUGH) {
+    NS_ERROR("Invalid decoration value!");
+    return path;
+  }
+
+  if (aParams.style != NS_STYLE_TEXT_DECORATION_STYLE_SOLID) {
+    // For the moment, we support only solid text decorations.
+    return path;
+  }
+
+  Float lineThickness = std::max(NS_round(aParams.lineSize.height), 1.0);
+
+  // The block-direction position should be set to the middle of the line.
+  if (aParams.vertical) {
+    rect.x += lineThickness / 2;
+    path = Rect(rect.TopLeft() - Point(lineThickness / 2, 0.0),
+                Size(lineThickness, rect.Height()));
+  } else {
+    rect.y += lineThickness / 2;
+    path = Rect(rect.TopLeft() - Point(0.0, lineThickness / 2),
+                Size(rect.Width(), lineThickness));
+  }
+
+  return path;
+}
+
+nsRect
+nsCSSRendering::GetTextDecorationRect(nsPresContext* aPresContext,
+                                      const DecorationRectParams& aParams)
+{
+  NS_ASSERTION(aPresContext, "aPresContext is null");
+  NS_ASSERTION(aParams.style != NS_STYLE_TEXT_DECORATION_STYLE_NONE,
+               "aStyle is none");
+
+  gfxRect rect = GetTextDecorationRectInternal(Point(0, 0), aParams);
+  // The rect values are already rounded to nearest device pixels.
+  nsRect r;
+  r.x = aPresContext->GfxUnitsToAppUnits(rect.X());
+  r.y = aPresContext->GfxUnitsToAppUnits(rect.Y());
+  r.width = aPresContext->GfxUnitsToAppUnits(rect.Width());
+  r.height = aPresContext->GfxUnitsToAppUnits(rect.Height());
+  return r;
+}
+
+gfxRect
+nsCSSRendering::GetTextDecorationRectInternal(const Point& aPt,
+                                              const DecorationRectParams& aParams)
+{
+  NS_ASSERTION(aParams.style <= NS_STYLE_TEXT_DECORATION_STYLE_WAVY,
+               "Invalid aStyle value");
+
+  if (aParams.style == NS_STYLE_TEXT_DECORATION_STYLE_NONE)
+    return gfxRect(0, 0, 0, 0);
+
+  bool canLiftUnderline = aParams.descentLimit >= 0.0;
+
+  gfxFloat iCoord = aParams.vertical ? aPt.y : aPt.x;
+  gfxFloat bCoord = aParams.vertical ? aPt.x : aPt.y;
+
+  // 'left' and 'right' are relative to the line, so for vertical writing modes
+  // they will actually become top and bottom of the rendered line.
+  // Similarly, aLineSize.width and .height are actually length and thickness
+  // of the line, which runs horizontally or vertically according to aVertical.
+  const gfxFloat left  = floor(iCoord + 0.5),
+                 right = floor(iCoord + aParams.lineSize.width + 0.5);
+
+  // We compute |r| as if for a horizontal text run, and then swap vertical
+  // and horizontal coordinates at the end if vertical was requested.
+  gfxRect r(left, 0, right - left, 0);
+
+  gfxFloat lineThickness = NS_round(aParams.lineSize.height);
+  lineThickness = std::max(lineThickness, 1.0);
+
+  gfxFloat ascent = NS_round(aParams.ascent);
+  gfxFloat descentLimit = floor(aParams.descentLimit);
+
+  gfxFloat suggestedMaxRectHeight = std::max(std::min(ascent, descentLimit), 1.0);
+  r.height = lineThickness;
+  if (aParams.style == NS_STYLE_TEXT_DECORATION_STYLE_DOUBLE) {
+    /**
+     *  We will draw double line as:
+     *
+     * +-------------------------------------------+
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+     * |                                           | ^
+     * |                                           | | gap
+     * |                                           | v
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+     * +-------------------------------------------+
+     */
+    gfxFloat gap = NS_round(lineThickness / 2.0);
+    gap = std::max(gap, 1.0);
+    r.height = lineThickness * 2.0 + gap;
+    if (canLiftUnderline) {
+      if (r.Height() > suggestedMaxRectHeight) {
+        // Don't shrink the line height, because the thickness has some meaning.
+        // We can just shrink the gap at this time.
+        r.height = std::max(suggestedMaxRectHeight, lineThickness * 2.0 + 1.0);
+      }
+    }
+  } else if (aParams.style == NS_STYLE_TEXT_DECORATION_STYLE_WAVY) {
+    /**
+     *  We will draw wavy line as:
+     *
+     * +-------------------------------------------+
+     * |XXXXX            XXXXXX            XXXXXX  | ^
+     * |XXXXXX          XXXXXXXX          XXXXXXXX | | lineThickness
+     * |XXXXXXX        XXXXXXXXXX        XXXXXXXXXX| v
+     * |     XXX      XXX      XXX      XXX      XX|
+     * |      XXXXXXXXXX        XXXXXXXXXX        X|
+     * |       XXXXXXXX          XXXXXXXX          |
+     * |        XXXXXX            XXXXXX           |
+     * +-------------------------------------------+
+     */
+    r.height = lineThickness > 2.0 ? lineThickness * 4.0 : lineThickness * 3.0;
+    if (canLiftUnderline) {
+      if (r.Height() > suggestedMaxRectHeight) {
+        // Don't shrink the line height even if there is not enough space,
+        // because the thickness has some meaning.  E.g., the 1px wavy line and
+        // 2px wavy line can be used for different meaning in IME selections
+        // at same time.
+        r.height = std::max(suggestedMaxRectHeight, lineThickness * 2.0);
+      }
+    }
+  }
+
+  gfxFloat baseline = floor(bCoord + aParams.ascent + 0.5);
+  gfxFloat offset = 0.0;
+  switch (aParams.decoration) {
+    case NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE:
+      offset = aParams.offset;
+      if (canLiftUnderline) {
+        if (descentLimit < -offset + r.Height()) {
+          // If we can ignore the offset and the decoration line is overflowing,
+          // we should align the bottom edge of the decoration line rect if it's
+          // possible.  Otherwise, we should lift up the top edge of the rect as
+          // far as possible.
+          gfxFloat offsetBottomAligned = -descentLimit + r.Height();
+          gfxFloat offsetTopAligned = 0.0;
+          offset = std::min(offsetBottomAligned, offsetTopAligned);
+        }
+      }
+      break;
+    case NS_STYLE_TEXT_DECORATION_LINE_OVERLINE:
+      offset = aParams.offset - lineThickness + r.Height();
+      break;
+    case NS_STYLE_TEXT_DECORATION_LINE_LINE_THROUGH: {
+      gfxFloat extra = floor(r.Height() / 2.0 + 0.5);
+      extra = std::max(extra, lineThickness);
+      offset = aParams.offset - lineThickness + extra;
+      break;
+    }
+    default:
+      NS_ERROR("Invalid decoration value!");
+  }
+
+  if (aParams.vertical) {
+    r.y = baseline + floor(offset + 0.5);
+    Swap(r.x, r.y);
+    Swap(r.width, r.height);
+  } else {
+    r.y = baseline - floor(offset + 0.5);
+  }
+
+  return r;
+}
+
+// ------------------
+// ImageRenderer
+// ------------------
+nsImageRenderer::nsImageRenderer(nsIFrame* aForFrame,
+                                 const nsStyleImage* aImage,
+                                 uint32_t aFlags)
+  : mForFrame(aForFrame)
+  , mImage(aImage)
+  , mType(aImage->GetType())
+  , mImageContainer(nullptr)
+  , mGradientData(nullptr)
+  , mPaintServerFrame(nullptr)
+  , mPrepareResult(DrawResult::NOT_READY)
+  , mSize(0, 0)
+  , mFlags(aFlags)
+  , mExtendMode(ExtendMode::CLAMP)
+  , mMaskOp(NS_STYLE_MASK_MODE_MATCH_SOURCE)
+{
+}
+
+nsImageRenderer::~nsImageRenderer()
+{
+}
+
+static bool
+ShouldTreatAsCompleteDueToSyncDecode(const nsStyleImage* aImage,
+                                     uint32_t aFlags)
+{
+  if (!(aFlags & nsImageRenderer::FLAG_SYNC_DECODE_IMAGES)) {
+    return false;
+  }
+
+  if (aImage->GetType() != eStyleImageType_Image) {
+    return false;
+  }
+
+  imgRequestProxy* req = aImage->GetImageData();
+  if (!req) {
+    return false;
+  }
+
+  uint32_t status = 0;
+  if (NS_FAILED(req->GetImageStatus(&status))) {
+    return false;
+  }
+
+  if (status & imgIRequest::STATUS_ERROR) {
+    // The image is "complete" since it's a corrupt image. If we created an
+    // imgIContainer at all, return true.
+    nsCOMPtr<imgIContainer> image;
+    req->GetImage(getter_AddRefs(image));
+    return bool(image);
+  }
+
+  if (!(status & imgIRequest::STATUS_LOAD_COMPLETE)) {
+    // We must have loaded all of the image's data and the size must be
+    // available, or else sync decoding won't be able to decode the image.
+    return false;
+  }
+
+  return true;
+}
+
+bool
+nsImageRenderer::PrepareImage()
+{
+  if (mImage->IsEmpty()) {
+    mPrepareResult = DrawResult::BAD_IMAGE;
+    return false;
+  }
+
+  if (!mImage->IsComplete()) {
+    // Make sure the image is actually decoding.
+    mImage->StartDecoding();
+
+    // Check again to see if we finished.
+    // We cannot prepare the image for rendering if it is not fully loaded.
+    // Special case: If we requested a sync decode and the image has loaded, push
+    // on through because the Draw() will do a sync decode then.
+    if (!mImage->IsComplete() &&
+        !ShouldTreatAsCompleteDueToSyncDecode(mImage, mFlags)) {
+      mPrepareResult = DrawResult::NOT_READY;
+      return false;
+    }
+  }
+
+  switch (mType) {
+    case eStyleImageType_Image: {
+      MOZ_ASSERT(mImage->GetImageData(),
+                 "must have image data, since we checked IsEmpty above");
+      nsCOMPtr<imgIContainer> srcImage;
+      DebugOnly<nsresult> rv =
+        mImage->GetImageData()->GetImage(getter_AddRefs(srcImage));
+      MOZ_ASSERT(NS_SUCCEEDED(rv) && srcImage,
+                 "If GetImage() is failing, mImage->IsComplete() "
+                 "should have returned false");
+
+      if (!mImage->GetCropRect()) {
+        mImageContainer.swap(srcImage);
+      } else {
+        nsIntRect actualCropRect;
+        bool isEntireImage;
+        bool success =
+          mImage->ComputeActualCropRect(actualCropRect, &isEntireImage);
+        NS_ASSERTION(success, "ComputeActualCropRect() should not fail here");
+        if (!success || actualCropRect.IsEmpty()) {
+          // The cropped image has zero size
+          mPrepareResult = DrawResult::BAD_IMAGE;
+          return false;
+        }
+        if (isEntireImage) {
+          // The cropped image is identical to the source image
+          mImageContainer.swap(srcImage);
+        } else {
+          nsCOMPtr<imgIContainer> subImage = ImageOps::Clip(srcImage,
+                                                            actualCropRect,
+                                                            Nothing());
+          mImageContainer.swap(subImage);
+        }
+      }
+      mPrepareResult = DrawResult::SUCCESS;
+      break;
+    }
+    case eStyleImageType_Gradient:
+      mGradientData = mImage->GetGradientData();
+      mPrepareResult = DrawResult::SUCCESS;
+      break;
+    case eStyleImageType_Element:
+    {
+      nsAutoString elementId =
+        NS_LITERAL_STRING("#") + nsDependentString(mImage->GetElementId());
+      nsCOMPtr<nsIURI> targetURI;
+      nsCOMPtr<nsIURI> base = mForFrame->GetContent()->GetBaseURI();
+      nsContentUtils::NewURIWithDocumentCharset(getter_AddRefs(targetURI), elementId,
+                                                mForFrame->GetContent()->GetUncomposedDoc(), base);
+      nsSVGPaintingProperty* property = nsSVGEffects::GetPaintingPropertyForURI(
+          targetURI, mForFrame->FirstContinuation(),
+          nsSVGEffects::BackgroundImageProperty());
+      if (!property) {
+        mPrepareResult = DrawResult::BAD_IMAGE;
+        return false;
+      }
+
+      // If the referenced element is an <img>, <canvas>, or <video> element,
+      // prefer SurfaceFromElement as it's more reliable.
+      mImageElementSurface =
+        nsLayoutUtils::SurfaceFromElement(property->GetReferencedElement());
+      if (!mImageElementSurface.GetSourceSurface()) {
+        nsIFrame* paintServerFrame = property->GetReferencedFrame();
+        // If there's no referenced frame, or the referenced frame is
+        // non-displayable SVG, then we have nothing valid to paint.
+        if (!paintServerFrame ||
+            (paintServerFrame->IsFrameOfType(nsIFrame::eSVG) &&
+             !paintServerFrame->IsFrameOfType(nsIFrame::eSVGPaintServer) &&
+             !static_cast<nsISVGChildFrame*>(do_QueryFrame(paintServerFrame)))) {
+          mPrepareResult = DrawResult::BAD_IMAGE;
+          return false;
+        }
+        mPaintServerFrame = paintServerFrame;
+      }
+
+      mPrepareResult = DrawResult::SUCCESS;
+      break;
+    }
+    case eStyleImageType_Null:
+    default:
+      break;
+  }
+
+  return IsReady();
+}
+
+nsSize
+CSSSizeOrRatio::ComputeConcreteSize() const
+{
+  NS_ASSERTION(CanComputeConcreteSize(), "Cannot compute");
+  if (mHasWidth && mHasHeight) {
+    return nsSize(mWidth, mHeight);
+  }
+  if (mHasWidth) {
+    nscoord height = NSCoordSaturatingNonnegativeMultiply(
+      mWidth,
+      double(mRatio.height) / mRatio.width);
+    return nsSize(mWidth, height);
+  }
+
+  MOZ_ASSERT(mHasHeight);
+  nscoord width = NSCoordSaturatingNonnegativeMultiply(
+    mHeight,
+    double(mRatio.width) / mRatio.height);
+  return nsSize(width, mHeight);
+}
+
+CSSSizeOrRatio
+nsImageRenderer::ComputeIntrinsicSize()
+{
+  NS_ASSERTION(IsReady(), "Ensure PrepareImage() has returned true "
+                          "before calling me");
+
+  CSSSizeOrRatio result;
+  switch (mType) {
+    case eStyleImageType_Image:
+    {
+      bool haveWidth, haveHeight;
+      CSSIntSize imageIntSize;
+      nsLayoutUtils::ComputeSizeForDrawing(mImageContainer, imageIntSize,
+                                           result.mRatio, haveWidth, haveHeight);
+      if (haveWidth) {
+        result.SetWidth(nsPresContext::CSSPixelsToAppUnits(imageIntSize.width));
+      }
+      if (haveHeight) {
+        result.SetHeight(nsPresContext::CSSPixelsToAppUnits(imageIntSize.height));
+      }
+      break;
+    }
+    case eStyleImageType_Element:
+    {
+      // XXX element() should have the width/height of the referenced element,
+      //     and that element's ratio, if it matches.  If it doesn't match, it
+      //     should have no width/height or ratio.  See element() in CSS images:
+      //     <http://dev.w3.org/csswg/css-images-4/#element-notation>.
+      //     Make sure to change nsStyleImageLayers::Size::DependsOnFrameSize
+      //     when fixing this!
+      if (mPaintServerFrame) {
+        // SVG images have no intrinsic size
+        if (!mPaintServerFrame->IsFrameOfType(nsIFrame::eSVG)) {
+          // The intrinsic image size for a generic nsIFrame paint server is
+          // the union of the border-box rects of all of its continuations,
+          // rounded to device pixels.
+          int32_t appUnitsPerDevPixel =
+            mForFrame->PresContext()->AppUnitsPerDevPixel();
+          result.SetSize(
+            IntSizeToAppUnits(
+              nsSVGIntegrationUtils::GetContinuationUnionSize(mPaintServerFrame).
+                ToNearestPixels(appUnitsPerDevPixel),
+              appUnitsPerDevPixel));
+        }
+      } else {
+        NS_ASSERTION(mImageElementSurface.GetSourceSurface(),
+                     "Surface should be ready.");
+        IntSize surfaceSize = mImageElementSurface.mSize;
+        result.SetSize(
+          nsSize(nsPresContext::CSSPixelsToAppUnits(surfaceSize.width),
+                 nsPresContext::CSSPixelsToAppUnits(surfaceSize.height)));
+      }
+      break;
+    }
+    case eStyleImageType_Gradient:
+      // Per <http://dev.w3.org/csswg/css3-images/#gradients>, gradients have no
+      // intrinsic dimensions.
+    case eStyleImageType_Null:
+    default:
+      break;
+  }
+
+  return result;
+}
+
+/* static */ nsSize
+nsImageRenderer::ComputeConcreteSize(const CSSSizeOrRatio& aSpecifiedSize,
+                                     const CSSSizeOrRatio& aIntrinsicSize,
+                                     const nsSize& aDefaultSize)
+{
+  // The specified size is fully specified, just use that
+  if (aSpecifiedSize.IsConcrete()) {
+    return aSpecifiedSize.ComputeConcreteSize();
+  }
+
+  MOZ_ASSERT(!aSpecifiedSize.mHasWidth || !aSpecifiedSize.mHasHeight);
+
+  if (!aSpecifiedSize.mHasWidth && !aSpecifiedSize.mHasHeight) {
+    // no specified size, try using the intrinsic size
+    if (aIntrinsicSize.CanComputeConcreteSize()) {
+      return aIntrinsicSize.ComputeConcreteSize();
+    }
+
+    if (aIntrinsicSize.mHasWidth) {
+      return nsSize(aIntrinsicSize.mWidth, aDefaultSize.height);
+    }
+    if (aIntrinsicSize.mHasHeight) {
+      return nsSize(aDefaultSize.width, aIntrinsicSize.mHeight);
+    }
+
+    // couldn't use the intrinsic size either, revert to using the default size
+    return ComputeConstrainedSize(aDefaultSize,
+                                  aIntrinsicSize.mRatio,
+                                  CONTAIN);
+  }
+
+  MOZ_ASSERT(aSpecifiedSize.mHasWidth || aSpecifiedSize.mHasHeight);
+
+  // The specified height is partial, try to compute the missing part.
+  if (aSpecifiedSize.mHasWidth) {
+    nscoord height;
+    if (aIntrinsicSize.HasRatio()) {
+      height = NSCoordSaturatingNonnegativeMultiply(
+        aSpecifiedSize.mWidth,
+        double(aIntrinsicSize.mRatio.height) / aIntrinsicSize.mRatio.width);
+    } else if (aIntrinsicSize.mHasHeight) {
+      height = aIntrinsicSize.mHeight;
+    } else {
+      height = aDefaultSize.height;
+    }
+    return nsSize(aSpecifiedSize.mWidth, height);
+  }
+
+  MOZ_ASSERT(aSpecifiedSize.mHasHeight);
+  nscoord width;
+  if (aIntrinsicSize.HasRatio()) {
+    width = NSCoordSaturatingNonnegativeMultiply(
+      aSpecifiedSize.mHeight,
+      double(aIntrinsicSize.mRatio.width) / aIntrinsicSize.mRatio.height);
+  } else if (aIntrinsicSize.mHasWidth) {
+    width = aIntrinsicSize.mWidth;
+  } else {
+    width = aDefaultSize.width;
+  }
+  return nsSize(width, aSpecifiedSize.mHeight);
+}
+
+/* static */ nsSize
+nsImageRenderer::ComputeConstrainedSize(const nsSize& aConstrainingSize,
+                                        const nsSize& aIntrinsicRatio,
+                                        FitType aFitType)
+{
+  if (aIntrinsicRatio.width <= 0 && aIntrinsicRatio.height <= 0) {
+    return aConstrainingSize;
+  }
+
+  float scaleX = double(aConstrainingSize.width) / aIntrinsicRatio.width;
+  float scaleY = double(aConstrainingSize.height) / aIntrinsicRatio.height;
+  nsSize size;
+  if ((aFitType == CONTAIN) == (scaleX < scaleY)) {
+    size.width = aConstrainingSize.width;
+    size.height = NSCoordSaturatingNonnegativeMultiply(
+                    aIntrinsicRatio.height, scaleX);
+    // If we're reducing the size by less than one css pixel, then just use the
+    // constraining size.
+    if (aFitType == CONTAIN && aConstrainingSize.height - size.height < nsPresContext::AppUnitsPerCSSPixel()) {
+      size.height = aConstrainingSize.height;
+    }
+  } else {
+    size.width = NSCoordSaturatingNonnegativeMultiply(
+                   aIntrinsicRatio.width, scaleY);
+    if (aFitType == CONTAIN && aConstrainingSize.width - size.width < nsPresContext::AppUnitsPerCSSPixel()) {
+      size.width = aConstrainingSize.width;
+    }
+    size.height = aConstrainingSize.height;
+  }
+  return size;
+}
+
+/**
+ * mSize is the image's "preferred" size for this particular rendering, while
+ * the drawn (aka concrete) size is the actual rendered size after accounting
+ * for background-size etc..  The preferred size is most often the image's
+ * intrinsic dimensions.  But for images with incomplete intrinsic dimensions,
+ * the preferred size varies, depending on the specified and default sizes, see
+ * nsImageRenderer::Compute*Size.
+ *
+ * This distinction is necessary because the components of a vector image are
+ * specified with respect to its preferred size for a rendering situation, not
+ * to its actual rendered size.  For example, consider a 4px wide background
+ * vector image with no height which contains a left-aligned
+ * 2px wide black rectangle with height 100%.  If the background-size width is
+ * auto (or 4px), the vector image will render 4px wide, and the black rectangle
+ * will be 2px wide.  If the background-size width is 8px, the vector image will
+ * render 8px wide, and the black rectangle will be 4px wide -- *not* 2px wide.
+ * In both cases mSize.width will be 4px; but in the first case the returned
+ * width will be 4px, while in the second case the returned width will be 8px.
+ */
+void
+nsImageRenderer::SetPreferredSize(const CSSSizeOrRatio& aIntrinsicSize,
+                                  const nsSize& aDefaultSize)
+{
+  mSize.width = aIntrinsicSize.mHasWidth
+                  ? aIntrinsicSize.mWidth
+                  : aDefaultSize.width;
+  mSize.height = aIntrinsicSize.mHasHeight
+                  ? aIntrinsicSize.mHeight
+                  : aDefaultSize.height;
+}
+
+// Convert from nsImageRenderer flags to the flags we want to use for drawing in
+// the imgIContainer namespace.
+static uint32_t
+ConvertImageRendererToDrawFlags(uint32_t aImageRendererFlags)
+{
+  uint32_t drawFlags = imgIContainer::FLAG_NONE;
+  if (aImageRendererFlags & nsImageRenderer::FLAG_SYNC_DECODE_IMAGES) {
+    drawFlags |= imgIContainer::FLAG_SYNC_DECODE;
+  }
+  if (aImageRendererFlags & nsImageRenderer::FLAG_PAINTING_TO_WINDOW) {
+    drawFlags |= imgIContainer::FLAG_HIGH_QUALITY_SCALING;
+  }
+  return drawFlags;
+}
+
+/*
+ *  SVG11: A luminanceToAlpha operation is equivalent to the following matrix operation:                                                   |
+ *  | R' |     |      0        0        0  0  0 |   | R |
+ *  | G' |     |      0        0        0  0  0 |   | G |
+ *  | B' |  =  |      0        0        0  0  0 | * | B |
+ *  | A' |     | 0.2125   0.7154   0.0721  0  0 |   | A |
+ *  | 1  |     |      0        0        0  0  1 |   | 1 |
+ */
+static void
+RGBALuminanceOperation(uint8_t *aData,
+                       int32_t aStride,
+                       const IntSize &aSize)
+{
+  int32_t redFactor = 55;    // 256 * 0.2125
+  int32_t greenFactor = 183; // 256 * 0.7154
+  int32_t blueFactor = 18;   // 256 * 0.0721
+
+  for (int32_t y = 0; y < aSize.height; y++) {
+    uint32_t *pixel = (uint32_t*)(aData + aStride * y);
+    for (int32_t x = 0; x < aSize.width; x++) {
+      *pixel = (((((*pixel & 0x00FF0000) >> 16) * redFactor) +
+                 (((*pixel & 0x0000FF00) >>  8) * greenFactor) +
+                  ((*pixel & 0x000000FF)        * blueFactor)) >> 8) << 24;
+      pixel++;
+    }
+  }
+}
+
+
+DrawResult
+nsImageRenderer::Draw(nsPresContext*       aPresContext,
+                      nsRenderingContext&  aRenderingContext,
+                      const nsRect&        aDirtyRect,
+                      const nsRect&        aDest,
+                      const nsRect&        aFill,
+                      const nsPoint&       aAnchor,
+                      const nsSize&        aRepeatSize,
+                      const CSSIntRect&    aSrc)
+{
+  if (!IsReady()) {
+    NS_NOTREACHED("Ensure PrepareImage() has returned true before calling me");
+    return DrawResult::TEMPORARY_ERROR;
+  }
+  if (aDest.IsEmpty() || aFill.IsEmpty() ||
+      mSize.width <= 0 || mSize.height <= 0) {
+    return DrawResult::SUCCESS;
+  }
+
+  SamplingFilter samplingFilter = nsLayoutUtils::GetSamplingFilterForFrame(mForFrame);
+  DrawResult result = DrawResult::SUCCESS;
+  RefPtr<gfxContext> ctx = aRenderingContext.ThebesContext();
+  IntRect tmpDTRect;
+
+  if (ctx->CurrentOp() != CompositionOp::OP_OVER || mMaskOp == NS_STYLE_MASK_MODE_LUMINANCE) {
+    gfxRect clipRect = ctx->GetClipExtents();
+    tmpDTRect = RoundedOut(ToRect(clipRect));
+    if (tmpDTRect.IsEmpty()) {
+      return DrawResult::SUCCESS;
+    }
+    RefPtr<DrawTarget> tempDT =
+      gfxPlatform::GetPlatform()->CreateSimilarSoftwareDrawTarget(ctx->GetDrawTarget(),
+                                                                  tmpDTRect.Size(),
+                                                                  SurfaceFormat::B8G8R8A8);
+    if (!tempDT || !tempDT->IsValid()) {
+      gfxDevCrash(LogReason::InvalidContext) << "ImageRenderer::Draw problem " << gfx::hexa(tempDT);
+      return DrawResult::TEMPORARY_ERROR;
+    }
+    tempDT->SetTransform(Matrix::Translation(-tmpDTRect.TopLeft()));
+    ctx = gfxContext::CreatePreservingTransformOrNull(tempDT);
+    if (!ctx) {
+      gfxDevCrash(LogReason::InvalidContext) << "ImageRenderer::Draw problem " << gfx::hexa(tempDT);
+      return DrawResult::TEMPORARY_ERROR;
+    }
+  }
+
+  switch (mType) {
+    case eStyleImageType_Image:
+    {
+      CSSIntSize imageSize(nsPresContext::AppUnitsToIntCSSPixels(mSize.width),
+                           nsPresContext::AppUnitsToIntCSSPixels(mSize.height));
+      result =
+        nsLayoutUtils::DrawBackgroundImage(*ctx,
+                                           aPresContext,
+                                           mImageContainer, imageSize,
+                                           samplingFilter,
+                                           aDest, aFill, aRepeatSize,
+                                           aAnchor, aDirtyRect,
+                                           ConvertImageRendererToDrawFlags(mFlags),
+                                           mExtendMode);
+      break;
+    }
+    case eStyleImageType_Gradient:
+    {
+      nsCSSRendering::PaintGradient(aPresContext, aRenderingContext,
+                                    mGradientData, aDirtyRect,
+                                    aDest, aFill, aRepeatSize, aSrc, mSize);
+      break;
+    }
+    case eStyleImageType_Element:
+    {
+      RefPtr<gfxDrawable> drawable = DrawableForElement(aDest,
+                                                          aRenderingContext);
+      if (!drawable) {
+        NS_WARNING("Could not create drawable for element");
+        return DrawResult::TEMPORARY_ERROR;
+      }
+
+      nsCOMPtr<imgIContainer> image(ImageOps::CreateFromDrawable(drawable));
+      result =
+        nsLayoutUtils::DrawImage(*ctx,
+                                 aPresContext, image,
+                                 samplingFilter, aDest, aFill, aAnchor, aDirtyRect,
+                                 ConvertImageRendererToDrawFlags(mFlags));
+      break;
+    }
+    case eStyleImageType_Null:
+    default:
+      break;
+  }
+
+  if (!tmpDTRect.IsEmpty()) {
+    RefPtr<SourceSurface> surf = ctx->GetDrawTarget()->Snapshot();
+    if (mMaskOp == NS_STYLE_MASK_MODE_LUMINANCE) {
+      RefPtr<DataSourceSurface> maskData = surf->GetDataSurface();
+      DataSourceSurface::MappedSurface map;
+      if (!maskData->Map(DataSourceSurface::MapType::WRITE, &map)) {
+        return result;
+      }
+
+      RGBALuminanceOperation(map.mData, map.mStride, maskData->GetSize());
+      maskData->Unmap();
+      surf = maskData;
+    }
+
+    DrawTarget* dt = aRenderingContext.ThebesContext()->GetDrawTarget();
+    dt->DrawSurface(surf, Rect(tmpDTRect.x, tmpDTRect.y, tmpDTRect.width, tmpDTRect.height),
+                    Rect(0, 0, tmpDTRect.width, tmpDTRect.height),
+                    DrawSurfaceOptions(SamplingFilter::POINT),
+                    DrawOptions(1.0f, aRenderingContext.ThebesContext()->CurrentOp()));
+  }
+
+  return result;
+}
+
+already_AddRefed<gfxDrawable>
+nsImageRenderer::DrawableForElement(const nsRect& aImageRect,
+                                    nsRenderingContext&  aRenderingContext)
+{
+  NS_ASSERTION(mType == eStyleImageType_Element,
+               "DrawableForElement only makes sense if backed by an element");
+  if (mPaintServerFrame) {
+    // XXX(seth): In order to not pass FLAG_SYNC_DECODE_IMAGES here,
+    // DrawableFromPaintServer would have to return a DrawResult indicating
+    // whether any images could not be painted because they weren't fully
+    // decoded. Even always passing FLAG_SYNC_DECODE_IMAGES won't eliminate all
+    // problems, as it won't help if there are image which haven't finished
+    // loading, but it's better than nothing.
+    int32_t appUnitsPerDevPixel = mForFrame->PresContext()->AppUnitsPerDevPixel();
+    nsRect destRect = aImageRect - aImageRect.TopLeft();
+    nsIntSize roundedOut = destRect.ToOutsidePixels(appUnitsPerDevPixel).Size();
+    IntSize imageSize(roundedOut.width, roundedOut.height);
+    RefPtr<gfxDrawable> drawable =
+      nsSVGIntegrationUtils::DrawableFromPaintServer(
+        mPaintServerFrame, mForFrame, mSize, imageSize,
+        aRenderingContext.GetDrawTarget(),
+        aRenderingContext.ThebesContext()->CurrentMatrix(),
+        nsSVGIntegrationUtils::FLAG_SYNC_DECODE_IMAGES);
+
+    return drawable.forget();
+  }
+  NS_ASSERTION(mImageElementSurface.GetSourceSurface(), "Surface should be ready.");
+  RefPtr<gfxDrawable> drawable = new gfxSurfaceDrawable(
+                                mImageElementSurface.GetSourceSurface().get(),
+                                mImageElementSurface.mSize);
+  return drawable.forget();
+}
+
+DrawResult
+nsImageRenderer::DrawBackground(nsPresContext*       aPresContext,
+                                nsRenderingContext&  aRenderingContext,
+                                const nsRect&        aDest,
+                                const nsRect&        aFill,
+                                const nsPoint&       aAnchor,
+                                const nsRect&        aDirty,
+                                const nsSize&        aRepeatSize)
+{
+  if (!IsReady()) {
+    NS_NOTREACHED("Ensure PrepareImage() has returned true before calling me");
+    return DrawResult::TEMPORARY_ERROR;
+  }
+  if (aDest.IsEmpty() || aFill.IsEmpty() ||
+      mSize.width <= 0 || mSize.height <= 0) {
+    return DrawResult::SUCCESS;
+  }
+
+  return Draw(aPresContext, aRenderingContext,
+              aDirty, aDest, aFill, aAnchor, aRepeatSize,
+              CSSIntRect(0, 0,
+                         nsPresContext::AppUnitsToIntCSSPixels(mSize.width),
+                         nsPresContext::AppUnitsToIntCSSPixels(mSize.height)));
+}
+
+/**
+ * Compute the size and position of the master copy of the image. I.e., a single
+ * tile used to fill the dest rect.
+ * aFill The destination rect to be filled
+ * aHFill and aVFill are the repeat patterns for the component -
+ * NS_STYLE_BORDER_IMAGE_REPEAT_* - i.e., how a tiling unit is used to fill aFill
+ * aUnitSize The size of the source rect in dest coords.
+ */
+static nsRect
+ComputeTile(nsRect&              aFill,
+            uint8_t              aHFill,
+            uint8_t              aVFill,
+            const nsSize&        aUnitSize,
+            nsSize&              aRepeatSize)
+{
+  nsRect tile;
+  switch (aHFill) {
+  case NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH:
+    tile.x = aFill.x;
+    tile.width = aFill.width;
+    aRepeatSize.width = tile.width;
+    break;
+  case NS_STYLE_BORDER_IMAGE_REPEAT_REPEAT:
+    tile.x = aFill.x + aFill.width/2 - aUnitSize.width/2;
+    tile.width = aUnitSize.width;
+    aRepeatSize.width = tile.width;
+    break;
+  case NS_STYLE_BORDER_IMAGE_REPEAT_ROUND:
+    tile.x = aFill.x;
+    tile.width = ComputeRoundedSize(aUnitSize.width, aFill.width);
+    aRepeatSize.width = tile.width;
+    break;
+  case NS_STYLE_BORDER_IMAGE_REPEAT_SPACE:
+    {
+      nscoord space;
+      aRepeatSize.width =
+        ComputeBorderSpacedRepeatSize(aUnitSize.width, aFill.width, space);
+      tile.x = aFill.x + space;
+      tile.width = aUnitSize.width;
+      aFill.x = tile.x;
+      aFill.width = aFill.width - space * 2;
+    }
+    break;
+  default:
+    NS_NOTREACHED("unrecognized border-image fill style");
+  }
+
+  switch (aVFill) {
+  case NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH:
+    tile.y = aFill.y;
+    tile.height = aFill.height;
+    aRepeatSize.height = tile.height;
+    break;
+  case NS_STYLE_BORDER_IMAGE_REPEAT_REPEAT:
+    tile.y = aFill.y + aFill.height/2 - aUnitSize.height/2;
+    tile.height = aUnitSize.height;
+    aRepeatSize.height = tile.height;
+    break;
+  case NS_STYLE_BORDER_IMAGE_REPEAT_ROUND:
+    tile.y = aFill.y;
+    tile.height = ComputeRoundedSize(aUnitSize.height, aFill.height);
+    aRepeatSize.height = tile.height;
+    break;
+  case NS_STYLE_BORDER_IMAGE_REPEAT_SPACE:
+    {
+      nscoord space;
+      aRepeatSize.height =
+        ComputeBorderSpacedRepeatSize(aUnitSize.height, aFill.height, space);
+      tile.y = aFill.y + space;
+      tile.height = aUnitSize.height;
+      aFill.y = tile.y;
+      aFill.height = aFill.height - space * 2;
+    }
+    break;
+  default:
+    NS_NOTREACHED("unrecognized border-image fill style");
+  }
+
+  return tile;
+}
+
+/**
+ * Returns true if the given set of arguments will require the tiles which fill
+ * the dest rect to be scaled from the source tile. See comment on ComputeTile
+ * for argument descriptions.
+ */
+static bool
+RequiresScaling(const nsRect&        aFill,
+                uint8_t              aHFill,
+                uint8_t              aVFill,
+                const nsSize&        aUnitSize)
+{
+  // If we have no tiling in either direction, we can skip the intermediate
+  // scaling step.
+  return (aHFill != NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH ||
+          aVFill != NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH) &&
+         (aUnitSize.width != aFill.width ||
+          aUnitSize.height != aFill.height);
+}
+
+DrawResult
+nsImageRenderer::DrawBorderImageComponent(nsPresContext*       aPresContext,
+                                          nsRenderingContext&  aRenderingContext,
+                                          const nsRect&        aDirtyRect,
+                                          const nsRect&        aFill,
+                                          const CSSIntRect&    aSrc,
+                                          uint8_t              aHFill,
+                                          uint8_t              aVFill,
+                                          const nsSize&        aUnitSize,
+                                          uint8_t              aIndex,
+                                          const Maybe<nsSize>& aSVGViewportSize,
+                                          const bool           aHasIntrinsicRatio)
+{
+  if (!IsReady()) {
+    NS_NOTREACHED("Ensure PrepareImage() has returned true before calling me");
+    return DrawResult::BAD_ARGS;
+  }
+  if (aFill.IsEmpty() || aSrc.IsEmpty()) {
+    return DrawResult::SUCCESS;
+  }
+
+  if (mType == eStyleImageType_Image || mType == eStyleImageType_Element) {
+    nsCOMPtr<imgIContainer> subImage;
+
+    // To draw one portion of an image into a border component, we stretch that
+    // portion to match the size of that border component and then draw onto.
+    // However, preserveAspectRatio attribute of a SVG image may break this rule.
+    // To get correct rendering result, we add
+    // FLAG_FORCE_PRESERVEASPECTRATIO_NONE flag here, to tell mImage to ignore
+    // preserveAspectRatio attribute, and always do non-uniform stretch.
+    uint32_t drawFlags = ConvertImageRendererToDrawFlags(mFlags) |
+                           imgIContainer::FLAG_FORCE_PRESERVEASPECTRATIO_NONE;
+    // For those SVG image sources which don't have fixed aspect ratio (i.e.
+    // without viewport size and viewBox), we should scale the source uniformly
+    // after the viewport size is decided by "Default Sizing Algorithm".
+    if (!aHasIntrinsicRatio) {
+      drawFlags = drawFlags | imgIContainer::FLAG_FORCE_UNIFORM_SCALING;
+    }
+    // Retrieve or create the subimage we'll draw.
+    nsIntRect srcRect(aSrc.x, aSrc.y, aSrc.width, aSrc.height);
+    if (mType == eStyleImageType_Image) {
+      if ((subImage = mImage->GetSubImage(aIndex)) == nullptr) {
+        subImage = ImageOps::Clip(mImageContainer, srcRect, aSVGViewportSize);
+        mImage->SetSubImage(aIndex, subImage);
+      }
+    } else {
+      // This path, for eStyleImageType_Element, is currently slower than it
+      // needs to be because we don't cache anything. (In particular, if we have
+      // to draw to a temporary surface inside ClippedImage, we don't cache that
+      // temporary surface since we immediately throw the ClippedImage we create
+      // here away.) However, if we did cache, we'd need to know when to
+      // invalidate that cache, and it's not clear that it's worth the trouble
+      // since using border-image with -moz-element is rare.
+
+      RefPtr<gfxDrawable> drawable = DrawableForElement(nsRect(nsPoint(), mSize),
+                                                          aRenderingContext);
+      if (!drawable) {
+        NS_WARNING("Could not create drawable for element");
+        return DrawResult::TEMPORARY_ERROR;
+      }
+
+      nsCOMPtr<imgIContainer> image(ImageOps::CreateFromDrawable(drawable));
+      subImage = ImageOps::Clip(image, srcRect, aSVGViewportSize);
+    }
+
+    MOZ_ASSERT_IF(aSVGViewportSize,
+                  subImage->GetType() == imgIContainer::TYPE_VECTOR);
+
+    SamplingFilter samplingFilter = nsLayoutUtils::GetSamplingFilterForFrame(mForFrame);
+
+    if (!RequiresScaling(aFill, aHFill, aVFill, aUnitSize)) {
+      return nsLayoutUtils::DrawSingleImage(*aRenderingContext.ThebesContext(),
+                                            aPresContext,
+                                            subImage,
+                                            samplingFilter,
+                                            aFill, aDirtyRect,
+                                            nullptr,
+                                            drawFlags);
+    }
+
+    nsSize repeatSize;
+    nsRect fillRect(aFill);
+    nsRect tile = ComputeTile(fillRect, aHFill, aVFill, aUnitSize, repeatSize);
+    CSSIntSize imageSize(srcRect.width, srcRect.height);
+    return nsLayoutUtils::DrawBackgroundImage(*aRenderingContext.ThebesContext(),
+                                              aPresContext,
+                                              subImage, imageSize, samplingFilter,
+                                              tile, fillRect, repeatSize,
+                                              tile.TopLeft(), aDirtyRect,
+                                              drawFlags,
+                                              ExtendMode::CLAMP);
+  }
+
+  nsSize repeatSize(aFill.Size());
+  nsRect fillRect(aFill);
+  nsRect destTile = RequiresScaling(fillRect, aHFill, aVFill, aUnitSize)
+                  ? ComputeTile(fillRect, aHFill, aVFill, aUnitSize, repeatSize)
+                  : fillRect;
+  return Draw(aPresContext, aRenderingContext, aDirtyRect, destTile,
+              fillRect, destTile.TopLeft(), repeatSize, aSrc);
+}
+
+bool
+nsImageRenderer::IsRasterImage()
+{
+  if (mType != eStyleImageType_Image || !mImageContainer)
+    return false;
+  return mImageContainer->GetType() == imgIContainer::TYPE_RASTER;
+}
+
+bool
+nsImageRenderer::IsAnimatedImage()
+{
+  if (mType != eStyleImageType_Image || !mImageContainer)
+    return false;
+  bool animated = false;
+  if (NS_SUCCEEDED(mImageContainer->GetAnimated(&animated)) && animated)
+    return true;
+
+  return false;
+}
+
+already_AddRefed<imgIContainer>
+nsImageRenderer::GetImage()
+{
+  if (mType != eStyleImageType_Image || !mImageContainer) {
+    return nullptr;
+  }
+
+  nsCOMPtr<imgIContainer> image = mImageContainer;
+  return image.forget();
+}
+
+void
+nsImageRenderer::PurgeCacheForViewportChange(
+  const Maybe<nsSize>& aSVGViewportSize, const bool aHasIntrinsicRatio)
+{
+  // Check if we should flush the cached data - only vector images need to do
+  // the check since they might not have fixed ratio.
+  if (mImageContainer &&
+      mImageContainer->GetType() == imgIContainer::TYPE_VECTOR) {
+    mImage->PurgeCacheForViewportChange(aSVGViewportSize, aHasIntrinsicRatio);
+  }
+}
+
+#define MAX_BLUR_RADIUS 300
+#define MAX_SPREAD_RADIUS 50
+
+static inline gfxPoint ComputeBlurStdDev(nscoord aBlurRadius,
+                                         int32_t aAppUnitsPerDevPixel,
+                                         gfxFloat aScaleX,
+                                         gfxFloat aScaleY)
+{
+  // http://dev.w3.org/csswg/css3-background/#box-shadow says that the
+  // standard deviation of the blur should be half the given blur value.
+  gfxFloat blurStdDev = gfxFloat(aBlurRadius) / gfxFloat(aAppUnitsPerDevPixel);
+
+  return gfxPoint(std::min((blurStdDev * aScaleX),
+                           gfxFloat(MAX_BLUR_RADIUS)) / 2.0,
+                  std::min((blurStdDev * aScaleY),
+                           gfxFloat(MAX_BLUR_RADIUS)) / 2.0);
+}
+
+static inline IntSize
+ComputeBlurRadius(nscoord aBlurRadius,
+                  int32_t aAppUnitsPerDevPixel,
+                  gfxFloat aScaleX = 1.0,
+                  gfxFloat aScaleY = 1.0)
+{
+  gfxPoint scaledBlurStdDev = ComputeBlurStdDev(aBlurRadius, aAppUnitsPerDevPixel,
+                                                aScaleX, aScaleY);
+  return
+    gfxAlphaBoxBlur::CalculateBlurRadius(scaledBlurStdDev);
+}
+
+// -----
+// nsContextBoxBlur
+// -----
+gfxContext*
+nsContextBoxBlur::Init(const nsRect& aRect, nscoord aSpreadRadius,
+                       nscoord aBlurRadius,
+                       int32_t aAppUnitsPerDevPixel,
+                       gfxContext* aDestinationCtx,
+                       const nsRect& aDirtyRect,
+                       const gfxRect* aSkipRect,
+                       uint32_t aFlags)
+{
+  if (aRect.IsEmpty()) {
+    mContext = nullptr;
+    return nullptr;
+  }
+
+  IntSize blurRadius;
+  IntSize spreadRadius;
+  GetBlurAndSpreadRadius(aDestinationCtx->GetDrawTarget(), aAppUnitsPerDevPixel,
+                         aBlurRadius, aSpreadRadius,
+                         blurRadius, spreadRadius);
+
+  mDestinationCtx = aDestinationCtx;
+
+  // If not blurring, draw directly onto the destination device
+  if (blurRadius.width <= 0 && blurRadius.height <= 0 &&
+      spreadRadius.width <= 0 && spreadRadius.height <= 0 &&
+      !(aFlags & FORCE_MASK)) {
+    mContext = aDestinationCtx;
+    return mContext;
+  }
+
+  // Convert from app units to device pixels
+  gfxRect rect = nsLayoutUtils::RectToGfxRect(aRect, aAppUnitsPerDevPixel);
+
+  gfxRect dirtyRect =
+    nsLayoutUtils::RectToGfxRect(aDirtyRect, aAppUnitsPerDevPixel);
+  dirtyRect.RoundOut();
+
+  gfxMatrix transform = aDestinationCtx->CurrentMatrix();
+  rect = transform.TransformBounds(rect);
+
+  mPreTransformed = !transform.IsIdentity();
+
+  // Create the temporary surface for blurring
+  dirtyRect = transform.TransformBounds(dirtyRect);
+  if (aSkipRect) {
+    gfxRect skipRect = transform.TransformBounds(*aSkipRect);
+    mContext = mAlphaBoxBlur.Init(rect, spreadRadius,
+                                  blurRadius, &dirtyRect, &skipRect);
+  } else {
+    mContext = mAlphaBoxBlur.Init(rect, spreadRadius,
+                                  blurRadius, &dirtyRect, nullptr);
+  }
+
+  if (mContext) {
+    // we don't need to blur if skipRect is equal to rect
+    // and mContext will be nullptr
+    mContext->Multiply(transform);
+  }
+  return mContext;
+}
+
+void
+nsContextBoxBlur::DoPaint()
+{
+  if (mContext == mDestinationCtx) {
+    return;
+  }
+
+  gfxContextMatrixAutoSaveRestore saveMatrix(mDestinationCtx);
+
+  if (mPreTransformed) {
+    mDestinationCtx->SetMatrix(gfxMatrix());
+  }
+
+  mAlphaBoxBlur.Paint(mDestinationCtx);
+}
+
+gfxContext*
+nsContextBoxBlur::GetContext()
+{
+  return mContext;
+}
+
+/* static */ nsMargin
+nsContextBoxBlur::GetBlurRadiusMargin(nscoord aBlurRadius,
+                                      int32_t aAppUnitsPerDevPixel)
+{
+  IntSize blurRadius = ComputeBlurRadius(aBlurRadius, aAppUnitsPerDevPixel);
+
+  nsMargin result;
+  result.top = result.bottom = blurRadius.height * aAppUnitsPerDevPixel;
+  result.left = result.right = blurRadius.width  * aAppUnitsPerDevPixel;
+  return result;
+}
+
+/* static */ void
+nsContextBoxBlur::BlurRectangle(gfxContext* aDestinationCtx,
+                                const nsRect& aRect,
+                                int32_t aAppUnitsPerDevPixel,
+                                RectCornerRadii* aCornerRadii,
+                                nscoord aBlurRadius,
+                                const Color& aShadowColor,
+                                const nsRect& aDirtyRect,
+                                const gfxRect& aSkipRect)
+{
+  DrawTarget& aDestDrawTarget = *aDestinationCtx->GetDrawTarget();
+
+  if (aRect.IsEmpty()) {
+    return;
+  }
+
+  Rect shadowGfxRect = NSRectToRect(aRect, aAppUnitsPerDevPixel);
+
+  if (aBlurRadius <= 0) {
+    ColorPattern color(ToDeviceColor(aShadowColor));
+    if (aCornerRadii) {
+      RefPtr<Path> roundedRect = MakePathForRoundedRect(aDestDrawTarget,
+                                                        shadowGfxRect,
+                                                        *aCornerRadii);
+      aDestDrawTarget.Fill(roundedRect, color);
+    } else {
+      aDestDrawTarget.FillRect(shadowGfxRect, color);
+    }
+    return;
+  }
+
+  gfxFloat scaleX = 1;
+  gfxFloat scaleY = 1;
+
+  // Do blurs in device space when possible.
+  // Chrome/Skia always does the blurs in device space
+  // and will sometimes get incorrect results (e.g. rotated blurs)
+  gfxMatrix transform = aDestinationCtx->CurrentMatrix();
+  // XXX: we could probably handle negative scales but for now it's easier just to fallback
+  if (!transform.HasNonAxisAlignedTransform() && transform._11 > 0.0 && transform._22 > 0.0) {
+    scaleX = transform._11;
+    scaleY = transform._22;
+    aDestinationCtx->SetMatrix(gfxMatrix());
+  } else {
+    transform = gfxMatrix();
+  }
+
+  gfxPoint blurStdDev = ComputeBlurStdDev(aBlurRadius, aAppUnitsPerDevPixel, scaleX, scaleY);
+
+  gfxRect dirtyRect =
+    nsLayoutUtils::RectToGfxRect(aDirtyRect, aAppUnitsPerDevPixel);
+  dirtyRect.RoundOut();
+
+  gfxRect shadowThebesRect = transform.TransformBounds(ThebesRect(shadowGfxRect));
+  dirtyRect = transform.TransformBounds(dirtyRect);
+  gfxRect skipRect = transform.TransformBounds(aSkipRect);
+
+  if (aCornerRadii) {
+    aCornerRadii->Scale(scaleX, scaleY);
+  }
+
+  gfxAlphaBoxBlur::BlurRectangle(aDestinationCtx,
+                                 shadowThebesRect,
+                                 aCornerRadii,
+                                 blurStdDev,
+                                 aShadowColor,
+                                 dirtyRect,
+                                 skipRect);
+}
+
+/* static */ void
+nsContextBoxBlur::GetBlurAndSpreadRadius(DrawTarget* aDestDrawTarget,
+                                         int32_t aAppUnitsPerDevPixel,
+                                         nscoord aBlurRadius,
+                                         nscoord aSpreadRadius,
+                                         IntSize& aOutBlurRadius,
+                                         IntSize& aOutSpreadRadius,
+                                         bool aConstrainSpreadRadius)
+{
+  // Do blurs in device space when possible.
+  // Chrome/Skia always does the blurs in device space
+  // and will sometimes get incorrect results (e.g. rotated blurs)
+  Matrix transform = aDestDrawTarget->GetTransform();
+  // XXX: we could probably handle negative scales but for now it's easier just to fallback
+  gfxFloat scaleX, scaleY;
+  if (transform.HasNonAxisAlignedTransform() || transform._11 <= 0.0 || transform._22 <= 0.0) {
+    scaleX = 1;
+    scaleY = 1;
+  } else {
+    scaleX = transform._11;
+    scaleY = transform._22;
+  }
+
+  // compute a large or smaller blur radius
+  aOutBlurRadius = ComputeBlurRadius(aBlurRadius, aAppUnitsPerDevPixel, scaleX, scaleY);
+  aOutSpreadRadius =
+      IntSize(int32_t(aSpreadRadius * scaleX / aAppUnitsPerDevPixel),
+              int32_t(aSpreadRadius * scaleY / aAppUnitsPerDevPixel));
+
+
+  if (aConstrainSpreadRadius) {
+    aOutSpreadRadius.width = std::min(aOutSpreadRadius.width, int32_t(MAX_SPREAD_RADIUS));
+    aOutSpreadRadius.height = std::min(aOutSpreadRadius.height, int32_t(MAX_SPREAD_RADIUS));
+  }
+}
+
+/* static */ bool
+nsContextBoxBlur::InsetBoxBlur(gfxContext* aDestinationCtx,
+                               Rect aDestinationRect,
+                               Rect aShadowClipRect,
+                               Color& aShadowColor,
+                               nscoord aBlurRadiusAppUnits,
+                               nscoord aSpreadDistanceAppUnits,
+                               int32_t aAppUnitsPerDevPixel,
+                               bool aHasBorderRadius,
+                               RectCornerRadii& aInnerClipRectRadii,
+                               Rect aSkipRect, Point aShadowOffset)
+{
+  if (aDestinationRect.IsEmpty()) {
+    mContext = nullptr;
+    return false;
+  }
+
+  gfxContextAutoSaveRestore autoRestore(aDestinationCtx);
+
+  IntSize blurRadius;
+  IntSize spreadRadius;
+  // Convert the blur and spread radius to device pixels
+  bool constrainSpreadRadius = false;
+  GetBlurAndSpreadRadius(aDestinationCtx->GetDrawTarget(), aAppUnitsPerDevPixel,
+                         aBlurRadiusAppUnits, aSpreadDistanceAppUnits,
+                         blurRadius, spreadRadius, constrainSpreadRadius);
+
+  // The blur and spread radius are scaled already, so scale all
+  // input data to the blur. This way, we don't have to scale the min
+  // inset blur to the invert of the dest context, then rescale it back
+  // when we draw to the destination surface.
+  gfxSize scale = aDestinationCtx->CurrentMatrix().ScaleFactors(true);
+  Matrix transform = ToMatrix(aDestinationCtx->CurrentMatrix());
+
+  // XXX: we could probably handle negative scales but for now it's easier just to fallback
+  if (!transform.HasNonAxisAlignedTransform() && transform._11 > 0.0 && transform._22 > 0.0) {
+    // If we don't have a rotation, we're pre-transforming all the rects.
+    aDestinationCtx->SetMatrix(gfxMatrix());
+  } else {
+    // Don't touch anything, we have a rotation.
+    transform = Matrix();
+  }
+
+  Rect transformedDestRect = transform.TransformBounds(aDestinationRect);
+  Rect transformedShadowClipRect = transform.TransformBounds(aShadowClipRect);
+  Rect transformedSkipRect = transform.TransformBounds(aSkipRect);
+
+  transformedDestRect.Round();
+  transformedShadowClipRect.Round();
+  transformedSkipRect.RoundIn();
+
+  for (size_t i = 0; i < 4; i++) {
+    aInnerClipRectRadii[i].width = std::floor(scale.width * aInnerClipRectRadii[i].width);
+    aInnerClipRectRadii[i].height = std::floor(scale.height * aInnerClipRectRadii[i].height);
+  }
+
+  mAlphaBoxBlur.BlurInsetBox(aDestinationCtx, transformedDestRect,
+                             transformedShadowClipRect,
+                             blurRadius, spreadRadius,
+                             aShadowColor, aHasBorderRadius,
+                             aInnerClipRectRadii, transformedSkipRect,
+                             aShadowOffset);
+  return true;
+}