Reland of duce copying of local data structures in GeometryMapper and PaintLayerClipper.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index 3e2f9593c55f7ba2573bbfbb03a283ad09f74936..09c7fea0c69a181f322a55459771b8bda6b7c644 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -555,11 +555,11 @@
   ClipRectsContext clipRectsContext(compositingAncestor, UncachedClipRects,
                                     IgnoreOverlayScrollbarSize);
   clipRectsContext.setIgnoreOverflowClip();
-  LayoutRect unsnappedParentClipRect =
-      m_owningLayer.clipper(PaintLayer::DoNotUseGeometryMapper)
-          .backgroundClipRect(clipRectsContext)
-          .rect();
-  IntRect parentClipRect = pixelSnappedIntRect(unsnappedParentClipRect);
+
+  ClipRect clipRect;
+  m_owningLayer.clipper(PaintLayer::DoNotUseGeometryMapper)
+      .calculateBackgroundClipRect(clipRectsContext, clipRect);
+  IntRect parentClipRect = pixelSnappedIntRect(clipRect.rect());
   owningLayerIsClipped = parentClipRect != LayoutRect::infiniteIntRect();
 
   // TODO(schenney): CSS clips are not applied to composited children, and
@@ -1152,20 +1152,23 @@
   ClipRectsContext clipRectsContext(compositingContainer,
                                     PaintingClipRectsIgnoringOverflowClip,
                                     IgnoreOverlayScrollbarSize);
-  IntRect parentClipRect = pixelSnappedIntRect(
-      m_owningLayer.clipper(PaintLayer::DoNotUseGeometryMapper)
-          .backgroundClipRect(clipRectsContext)
-          .rect());
-  ASSERT(parentClipRect != LayoutRect::infiniteIntRect());
-  m_ancestorClippingLayer->setPosition(
-      FloatPoint(parentClipRect.location() - graphicsLayerParentLocation));
-  m_ancestorClippingLayer->setSize(FloatSize(parentClipRect.size()));
+
+  ClipRect parentClipRect;
+  m_owningLayer.clipper(PaintLayer::DoNotUseGeometryMapper)
+      .calculateBackgroundClipRect(clipRectsContext, parentClipRect);
+
+  IntRect snappedParentClipRect(pixelSnappedIntRect(parentClipRect.rect()));
+
+  DCHECK(snappedParentClipRect != LayoutRect::infiniteIntRect());
+  m_ancestorClippingLayer->setPosition(FloatPoint(
+      snappedParentClipRect.location() - graphicsLayerParentLocation));
+  m_ancestorClippingLayer->setSize(FloatSize(snappedParentClipRect.size()));
 
   // backgroundRect is relative to compositingContainer, so subtract
   // snappedOffsetFromCompositedAncestor.X/snappedOffsetFromCompositedAncestor.Y
   // to get back to local coords.
   m_ancestorClippingLayer->setOffsetFromLayoutObject(
-      parentClipRect.location() - snappedOffsetFromCompositedAncestor);
+      snappedParentClipRect.location() - snappedOffsetFromCompositedAncestor);
 
   if (m_ancestorClippingMaskLayer) {
     m_ancestorClippingMaskLayer->setOffsetFromLayoutObject(
@@ -1176,7 +1179,7 @@
 
   // The primary layer is then parented in, and positioned relative to this
   // clipping layer.
-  graphicsLayerParentLocation = parentClipRect.location();
+  graphicsLayerParentLocation = snappedParentClipRect.location();
 }
 
 void CompositedLayerMapping::updateOverflowControlsHostLayerGeometry(
@@ -2876,17 +2879,18 @@
   // these clip rects or otherwise optimizing.
   ClipRectsContext clipRectsContext(ancestorPaintInfo->paintLayer,
                                     UncachedClipRects);
-  IntRect parentClipRect = pixelSnappedIntRect(
-      paintInfo.paintLayer->clipper(PaintLayer::DoNotUseGeometryMapper)
-          .backgroundClipRect(clipRectsContext)
-          .rect());
-  ASSERT(parentClipRect != LayoutRect::infiniteIntRect());
+  ClipRect parentClipRect;
+  paintInfo.paintLayer->clipper(PaintLayer::DoNotUseGeometryMapper)
+      .calculateBackgroundClipRect(clipRectsContext, parentClipRect);
+
+  IntRect snappedParentClipRect(pixelSnappedIntRect(parentClipRect.rect()));
+  DCHECK(snappedParentClipRect != LayoutRect::infiniteIntRect());
 
   // Convert from ancestor to local coordinates.
   IntSize ancestorToLocalOffset = paintInfo.offsetFromLayoutObject -
                                   ancestorPaintInfo->offsetFromLayoutObject;
-  parentClipRect.move(ancestorToLocalOffset);
-  return parentClipRect;
+  snappedParentClipRect.move(ancestorToLocalOffset);
+  return snappedParentClipRect;
 }
 
 void CompositedLayerMapping::doPaintTask(