Clean up ancestorScrollingLayer

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 1070 matching lines @@
         return const_cast<RenderLayer*>(this);
 
     for (const RenderLayer* curr = compositingContainer(); curr; curr = curr->compositingContainer()) {
         if (curr->isRepaintContainer())
             return const_cast<RenderLayer*>(curr);
     }
 
     return 0;
 }
 
-RenderLayer* RenderLayer::ancestorCompositedScrollingLayer() const
-{
-    if (!compositor()->acceleratedCompositingForOverflowScrollEnabled())
-        return 0;
-
-    RenderObject* containingBlock = renderer()->containingBlock();
-    if (!containingBlock)
-        return 0;
-
-    RenderLayer* ancestorCompositedScrollingLayer = 0;
-    for (RenderLayer* ancestorLayer = containingBlock->enclosingLayer(); ancestorLayer; ancestorLayer = ancestorLayer->parent()) {
-        if (ancestorLayer->needsCompositedScrolling()) {
-            ancestorCompositedScrollingLayer = ancestorLayer;
-            break;
-        }
-    }
-
-    return ancestorCompositedScrollingLayer;
-}
-
 RenderLayer* RenderLayer::ancestorScrollingLayer() const
 {
-    RenderObject* containingBlock = renderer()->containingBlock();
-    if (!containingBlock)
-        return 0;
-
-    for (RenderLayer* ancestorLayer = containingBlock->enclosingLayer(); ancestorLayer; ancestorLayer = ancestorLayer->parent()) {
-        if (ancestorLayer->scrollsOverflow())
-            return ancestorLayer;
+    for (RenderObject* container = renderer()->containingBlock(); container; container = container->containingBlock()) {
+        RenderLayer* currentLayer = container->enclosingLayer();
+        if (currentLayer->scrollsOverflow())
+            return currentLayer;
     }
 
     return 0;
 }
 
 RenderLayer* RenderLayer::enclosingFilterLayer(IncludeSelfOrNot includeSelf) const
 {
     const RenderLayer* curr = (includeSelf == IncludeSelf) ? this : parent();
     for (; curr; curr = curr->parent()) {
         if (curr->requiresFullLayerImageForFilters())
@@ skipping 484 matching lines @@
     // layer as our 'scrolling ancestor'.
     //
     // Now, if we reside in a normal flow list, then we will naturally scroll with our scrolling
     // ancestor, and we need not be composited. If, on the other hand, we reside in a z-order
     // list, and on our walk upwards to our scrolling ancestor we find no layer that is a stacking
     // context, then we know that in the stacking tree, we will not be in the subtree rooted at
     // our scrolling ancestor, and we will therefore not scroll with it. In this case, we must
     // be a composited layer since the compositor will need to take special measures to ensure
     // that we scroll with our scrolling ancestor and it cannot do this if we do not promote.
 
-    RenderLayer* scrollParent = ancestorCompositedScrollingLayer();
+    RenderLayer* scrollParent = ancestorScrollingLayer();
     if (!scrollParent || scrollParent->stackingNode()->isStackingContext())
         return 0;
 
     // If we hit a stacking context on our way up to the ancestor scrolling layer, it will already
     // be composited due to an overflow scrolling parent, so we don't need to.
     for (RenderLayer* ancestor = parent(); ancestor && ancestor != scrollParent; ancestor = ancestor->parent()) {
         if (ancestor->stackingNode()->isStackingContext()) {
             scrollParent = 0;
             break;
         }
@@ skipping 2231 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif