Make composited scrolling codepaths co-operate.

Source/core/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 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 317 matching lines @@
     if (!m_needsUpdateCompositingRequirementsState)
         return;
 
     TRACE_EVENT0("blink_rendering,comp-scroll", "RenderLayerCompositor::updateCompositingRequirementsState");
 
     m_needsUpdateCompositingRequirementsState = false;
 
     if (!rootRenderLayer() || !rootRenderLayer()->acceleratedCompositingForOverflowScrollEnabled())
         return;
 
-    const bool compositorDrivenAcceleratedScrollingEnabled = rootRenderLayer()->compositorDrivenAcceleratedScrollingEnabled();
-
-    const FrameView::ScrollableAreaSet* scrollableAreas = m_renderView->frameView()->scrollableAreas();
-    if (!compositorDrivenAcceleratedScrollingEnabled && !scrollableAreas)
-        return;
-
     for (HashSet<RenderLayer*>::iterator it = m_outOfFlowPositionedLayers.begin(); it != m_outOfFlowPositionedLayers.end(); ++it)
         (*it)->updateHasUnclippedDescendant();
 
-    if (!compositorDrivenAcceleratedScrollingEnabled) {
-        for (FrameView::ScrollableAreaSet::iterator it = scrollableAreas->begin(); it != scrollableAreas->end(); ++it)
-            (*it)->updateNeedsCompositedScrolling();
-    }
+    const FrameView::ScrollableAreaSet* scrollableAreas = m_renderView->frameView()->scrollableAreas();
+    if (!scrollableAreas)
+        return;
+
+    for (FrameView::ScrollableAreaSet::iterator it = scrollableAreas->begin(); it != scrollableAreas->end(); ++it)
+        (*it)->updateNeedsCompositedScrolling();
 }
 
 void RenderLayerCompositor::updateCompositingLayers(CompositingUpdateType updateType, RenderLayer* updateRoot)
 {
     // Avoid updating the layers with old values. Compositing layers will be updated after the layout is finished.
     if (m_renderView->needsLayout())
         return;
 
     if (m_forceCompositingMode && !m_compositing)
         enableCompositingMode(true);
@@ skipping 1638 matching lines @@
     return renderer->hasFilter();
 }
 
 bool RenderLayerCompositor::requiresCompositingForBlending(RenderObject* renderer) const
 {
     return renderer->hasBlendMode();
 }
 
 bool RenderLayerCompositor::requiresCompositingForOverflowScrollingParent(const RenderLayer* layer) const
 {
-    if (!layer->compositorDrivenAcceleratedScrollingEnabled())
+    if (!layer->useCompositorDrivenAcceleratedScrolling())
         return false;
 
     // A layer scrolls with its containing block. So to find the overflow scrolling layer
     // that we scroll with respect to, we must ascend the layer tree until we reach the
     // first overflow scrolling div at or above our containing block. I will refer to this
     // 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
@@ skipping 744 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore