Invalidate scrolling contents on scrolling contents layer only

third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 389 matching lines @@
         layer()->compositedLayerMapping()->setContentsNeedDisplayInRect(r, invalidationReason);
     }
 }
 
 void LayoutBoxModelObject::invalidateDisplayItemClientOnBacking(const DisplayItemClientWrapper& displayItemClient, PaintInvalidationReason invalidationReason, const LayoutRect& previousPaintInvalidationRect, const LayoutRect& newPaintInvalidationRect) const
 {
     if (layer()->groupedMapping()) {
         if (GraphicsLayer* squashingLayer = layer()->groupedMapping()->squashingLayer())
             squashingLayer->invalidateDisplayItemClient(displayItemClient, invalidationReason, enclosingIntRect(previousPaintInvalidationRect), enclosingIntRect(newPaintInvalidationRect));
     } else if (CompositedLayerMapping* compositedLayerMapping = layer()->compositedLayerMapping()) {
-        compositedLayerMapping->invalidateDisplayItemClient(displayItemClient, invalidationReason, previousPaintInvalidationRect, newPaintInvalidationRect);
+        if (this->displayItemClient() != displayItemClient.displayItemClient() && isBox() && toLayoutBox(this)->usesCompositedScrolling())

[chrishtr, 2015/10/16 17:44:13]

Add a comment explaining this conditional.

[Xianzhu, 2015/10/16 17:52:06]

Done.

+            compositedLayerMapping->invalidateDisplayItemClientOnScrollingContentsLayer(displayItemClient, invalidationReason, previousPaintInvalidationRect, newPaintInvalidationRect);
+        else
+            compositedLayerMapping->invalidateDisplayItemClient(displayItemClient, invalidationReason, previousPaintInvalidationRect, newPaintInvalidationRect);
     }
 }
 
 void LayoutBoxModelObject::addOutlineRectsForNormalChildren(Vector<LayoutRect>& rects, const LayoutPoint& additionalOffset, IncludeBlockVisualOverflowOrNot includeBlockOverflows) const
 {
     for (LayoutObject* child = slowFirstChild(); child; child = child->nextSibling()) {
         // Outlines of out-of-flow positioned descendants are handled in LayoutBlock::addOutlineRects().
         if (child->isOutOfFlowPositioned())
             continue;
 
@@ skipping 629 matching lines @@
     if (rootElementStyle->hasBackground())
         return false;
 
     if (node() != document().firstBodyElement())
         return false;
 
     return true;
 }
 
 } // namespace blink