Revert 114283 - Avoid using backing store for compositing layers that just need to clip

Source/WebCore/rendering/RenderLayerCompositor.cpp

Index: Source/WebCore/rendering/RenderLayerCompositor.cpp
===================================================================
--- Source/WebCore/rendering/RenderLayerCompositor.cpp	(revision 115913)
+++ Source/WebCore/rendering/RenderLayerCompositor.cpp	(working copy)
@@ -584,7 +584,7 @@
 
     setCompositingParent(child, 0);
     
-    RenderLayer* compLayer = parent->enclosingCompositingLayerForRepaint();
+    RenderLayer* compLayer = parent->enclosingCompositingLayer();
     if (compLayer) {
         ASSERT(compLayer->backing());
         LayoutRect compBounds = child->backing()->compositedBounds();
@@ -1203,7 +1203,7 @@
 void RenderLayerCompositor::recursiveRepaintLayerRect(RenderLayer* layer, const IntRect& rect)
 {
     // FIXME: This method does not work correctly with transforms.
-    if (layer->isComposited() && !layer->backing()->paintsIntoCompositedAncestor())
+    if (layer->isComposited())
         layer->setBackingNeedsRepaintInRect(rect);
 
 #if !ASSERT_DISABLED
@@ -1398,15 +1398,15 @@
     }
     // The root layer always has a compositing layer, but it may not have backing.
     return requiresCompositingForTransform(renderer)
-        || requiresCompositingForVideo(renderer)
-        || requiresCompositingForCanvas(renderer)
-        || requiresCompositingForPlugin(renderer)
-        || requiresCompositingForFrame(renderer)
-        || (canRender3DTransforms() && renderer->style()->backfaceVisibility() == BackfaceVisibilityHidden)
-        || clipsCompositingDescendants(layer)
-        || requiresCompositingForAnimation(renderer)
-        || requiresCompositingForFilters(renderer)
-        || requiresCompositingForPosition(renderer, layer);
+             || requiresCompositingForVideo(renderer)
+             || requiresCompositingForCanvas(renderer)
+             || requiresCompositingForPlugin(renderer)
+             || requiresCompositingForFrame(renderer)
+             || (canRender3DTransforms() && renderer->style()->backfaceVisibility() == BackfaceVisibilityHidden)
+             || clipsCompositingDescendants(layer)
+             || requiresCompositingForAnimation(renderer)
+             || requiresCompositingForFilters(renderer)
+             || requiresCompositingForPosition(renderer, layer);
 }
 
 bool RenderLayerCompositor::canBeComposited(const RenderLayer* layer) const
@@ -1414,32 +1414,6 @@
     return m_hasAcceleratedCompositing && layer->isSelfPaintingLayer();
 }
 
-bool RenderLayerCompositor::requiresOwnBackingStore(const RenderLayer* layer, const RenderLayer* compositingAncestorLayer) const
-{
-    RenderObject* renderer = layer->renderer();
-    if (compositingAncestorLayer
-        && !(compositingAncestorLayer->backing()->graphicsLayer()->drawsContent()
-            || compositingAncestorLayer->backing()->paintsIntoWindow()
-            || compositingAncestorLayer->backing()->paintsIntoCompositedAncestor()))
-        return true;
-
-    return layer->isRootLayer()
-        || layer->transform() // note: excludes perspective and transformStyle3D.
-        || requiresCompositingForVideo(renderer)
-        || requiresCompositingForCanvas(renderer)
-        || requiresCompositingForPlugin(renderer)
-        || requiresCompositingForFrame(renderer)
-        || (canRender3DTransforms() && renderer->style()->backfaceVisibility() == BackfaceVisibilityHidden)
-        || requiresCompositingForAnimation(renderer)
-        || requiresCompositingForFilters(renderer)
-        || requiresCompositingForPosition(renderer, layer)
-        || renderer->isTransparent()
-        || renderer->hasMask()
-        || renderer->hasReflection()
-        || renderer->hasFilter()
-        || layer->mustOverlapCompositedLayers();
-}
-
 #if !LOG_DISABLED
 const char* RenderLayerCompositor::reasonForCompositing(const RenderLayer* layer)
 {