Remove document.rootScroller compositing clipping effects.

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

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 520 matching lines @@
     return;
 
   const LayoutBoxModelObject* clippingContainer =
       m_owningLayer.clippingContainer();
   if (!clippingContainer)
     return;
 
   if (clippingContainer->enclosingLayer() == scrollParent)
     return;
 
-  if (clippingContainer->enclosingLayer()->hasRootScrollerAsDescendant())
-    return;
-
   if (compositingAncestor->layoutObject().isDescendantOf(clippingContainer))
     return;
 
   // We ignore overflow clip here; we want composited overflow content to
   // behave as if it lives in an unclipped universe so it can prepaint, etc.
   // This means that we need to check if we are actually clipped before
   // setting up m_ancestorClippingLayer otherwise
   // updateAncestorClippingLayerGeometry will fail as the clip rect will be
   // infinite.
   // FIXME: this should use cached clip rects, but this sometimes give
@@ skipping 49 matching lines @@
           compositor->needsContentsCompositingLayer(&m_owningLayer)))
     layerConfigChanged = true;
 
   bool needsDescendantsClippingLayer =
       compositor->clipsCompositingDescendants(&m_owningLayer);
 
   // Our scrolling layer will clip.
   if (m_owningLayer.needsCompositedScrolling())
     needsDescendantsClippingLayer = false;
 
-  // We disable clipping on ancestor layers of the root scroller to give it
-  // the same behavior w.r.t browser controls as the real root layer. See the
-  // RootScrollerController class for more details.
-  if (m_owningLayer.hasRootScrollerAsDescendant())
-    needsDescendantsClippingLayer = false;
-
   const PaintLayer* scrollParent = this->scrollParent();
 
   // This is required because compositing layers are parented according to the
   // z-order hierarchy, yet clipping goes down the layoutObject hierarchy. Thus,
   // a PaintLayer can be clipped by a PaintLayer that is an ancestor in the
   // layoutObject hierarchy, but a sibling in the z-order hierarchy. Further,
   // that sibling need not be composited at all. In such scenarios, an ancestor
   // clipping layer is necessary to apply the composited clip for this layer.
   bool needsAncestorClip = false;
   bool needsAncestorClippingMask = false;
@@ skipping 1665 matching lines @@
   ScrollingCoordinator* scrollingCoordinator =
       scrollingCoordinatorFromLayer(m_owningLayer);
 
   bool layerChanged = false;
   if (needsScrollingLayers) {
     if (!m_scrollingLayer) {
       // Outer layer which corresponds with the scroll view.
       m_scrollingLayer =
           createGraphicsLayer(CompositingReasonLayerForScrollingContainer);
       m_scrollingLayer->setDrawsContent(false);
+      m_scrollingLayer->setMasksToBounds(true);
 
       // Inner layer which renders the content that scrolls.
       m_scrollingContentsLayer =
           createGraphicsLayer(CompositingReasonLayerForScrollingContents);
 
       if (Node* owningNode = m_owningLayer.layoutObject().node())
         m_scrollingContentsLayer->setElementId(createCompositorElementId(
             DOMNodeIds::idForNode(owningNode), CompositorSubElementId::Scroll));
 
       m_scrollingLayer->addChild(m_scrollingContentsLayer.get());
 
       layerChanged = true;
       if (scrollingCoordinator) {
         scrollingCoordinator->scrollableAreaScrollLayerDidChange(
             m_owningLayer.getScrollableArea());
         scrollingCoordinator->scrollableAreasDidChange();
       }
     }
-
-    m_scrollingLayer->setMasksToBounds(
-        !m_owningLayer.hasRootScrollerAsDescendant());
   } else if (m_scrollingLayer) {
     m_scrollingLayer = nullptr;
     m_scrollingContentsLayer = nullptr;
     layerChanged = true;
     if (scrollingCoordinator) {
       scrollingCoordinator->scrollableAreaScrollLayerDidChange(
           m_owningLayer.getScrollableArea());
       scrollingCoordinator->scrollableAreasDidChange();
     }
   }
@@ skipping 1174 matching lines @@
   } else if (graphicsLayer == m_decorationOutlineLayer.get()) {
     name = "Decoration Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink