Apply offset from the correct graphics layer; simplify code for link highlights.

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 2146ec37fff702c9672c646f6c04d27b07ea09eb..5e4aa2e0aa0f6b6283e68a6d9a4b2eb6e4d102fa 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -548,11 +548,8 @@ void PaintLayer::mapPointInPaintInvalidationContainerToBacking(
     const LayoutBoxModelObject& paintInvalidationContainer,
     FloatPoint& point) {
   PaintLayer* paintInvalidationLayer = paintInvalidationContainer.layer();
-  if (!paintInvalidationLayer->groupedMapping()) {
-    point.move(paintInvalidationLayer->compositedLayerMapping()
-                   ->contentOffsetInCompositingLayer());

[Xianzhu, 2016/12/29 05:48:12]

Was confused by this when working on VisualRectMappingTest for spinvalidation.
Glad to see this gone.

[Xianzhu, 2016/12/29 06:33:00]

I just paused CQ because of a question:

Is there any caller depending on the behavior of the above removed lines?

- Many callers like the following seem fine:
  if (paintInvalidationContainer.layer()->groupedMapping())
    mapPointInPaintInvalidationContainerToBacking(...)

- LinkHighlightImpl should expect the behavior change;

- I'm not sure about LayoutObject::localToInvalidationBackingPoint(). One
callsite is FrameView::computeCompositedSelection(). Can you verify if the
behavior change for these callsites are OK?

Also we may need a followup to also remove the similar offset in
mapRectInPaintInvalidationContainerToBacking(), verify callsites, and (maybe
optionally) simplify callsites by removing the redundant groupdMapping() check.

[chrishtr, 2016/12/29 16:53:04]

This one is not ok. Re-inserted this line. As you mention, only one call
site triggers this after my patch.
Will follow up with other patches along these lines.

+  if (!paintInvalidationLayer->groupedMapping())
     return;
-  }
 
   LayoutBoxModelObject* transformedAncestor =
       paintInvalidationLayer->enclosingTransformedAncestor()->layoutObject();