Use unfragmented clip bounds when fragmentation is inhibited due to compositing

third_party/WebKit/Source/core/paint/PaintLayer.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index 37f7d4a580967fc64ff1f5eee3e033bbee52aad5..c001d1c055d3172fd41b649ec6e717bd49b82f3d 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -1133,7 +1133,7 @@ LayoutRect PaintLayer::transparencyClipBox(const PaintLayer* layer, const PaintL
         return result;
     }
 
-    LayoutRect clipRect = layer->fragmentsBoundingBox(rootLayer);
+    LayoutRect clipRect = layer->shouldFragmentCompositedBounds(rootLayer) ? layer->fragmentsBoundingBox(rootLayer) : layer->physicalBoundingBox(rootLayer);
     expandClipRectForDescendantsAndReflection(clipRect, layer, rootLayer, transparencyBehavior, subPixelAccumulation, globalPaintFlags);
     clipRect = layer->mapLayoutRectForFilter(clipRect);
     clipRect.move(subPixelAccumulation);
@@ -2164,6 +2164,9 @@ LayoutRect PaintLayer::boundingBoxForCompositingOverlapTest() const
 {
     // Apply NeverIncludeTransformForAncestorLayer, because the geometry map in CompositingInputsUpdater will take care of applying the
     // transform of |this| (== the ancestorLayer argument to boundingBoxForCompositing).
+    // TODO(trchen): Layer fragmentation is inhibited across compositing boundary. Should we
+    // return the unfragmented bounds for overlap testing? Or perhaps assume fragmented layers
+    // always overlap?
     return overlapBoundsIncludeChildren() ? boundingBoxForCompositing(this, NeverIncludeTransformForAncestorLayer) : fragmentsBoundingBox(this);
 }