Use a boolean hasCompositedLayerMapping() accessor instead of the pointer

Source/core/testing/Internals.cpp

Index: Source/core/testing/Internals.cpp
diff --git a/Source/core/testing/Internals.cpp b/Source/core/testing/Internals.cpp
index bad025393980c4db3519338174a074dce763b326..b454f70a7c5479b00895c0c2ea08949f088e5df0 100644
--- a/Source/core/testing/Internals.cpp
+++ b/Source/core/testing/Internals.cpp
@@ -1270,7 +1270,9 @@ unsigned Internals::touchEventHandlerCount(Document* document, ExceptionState& e
 
 static RenderLayer* findRenderLayerForGraphicsLayer(RenderLayer* searchRoot, GraphicsLayer* graphicsLayer, String* layerType)
 {
-    if (searchRoot->compositedLayerMapping() && graphicsLayer == searchRoot->compositedLayerMapping()->mainGraphicsLayer())
+    // Note, we only want to return the RenderLayer that _truly_ owns the GraphicsLayer, not just the
+    // first RenderLayer we encounter that paints into it.
+    if (searchRoot->compositingState() == PaintsIntoOwnBacking && graphicsLayer == searchRoot->compositedLayerMapping()->mainGraphicsLayer())

[shawnsingh, 2013/11/12 21:12:50]

Option 1: maybe we should keep this as hasCompositedLayerMapping for now

Option 2: can you please explain why it should not be true when
HasOwnBackingButPaintsIntoAncestor?  based on the comment, it should include
that condition.  the mainGraphicsLayer will still exist for composited
RenderLayers that paint into ancestor.

         return searchRoot;
 
     GraphicsLayer* layerForScrolling = searchRoot->scrollableArea() ? searchRoot->scrollableArea()->layerForScrolling() : 0;
@@ -1753,7 +1755,7 @@ String Internals::elementLayerTreeAsText(Element* element, unsigned flags, Excep
 
     RenderLayer* layer = toRenderBox(renderer)->layer();
     if (!layer
-        || !layer->compositedLayerMapping()
+        || !layer->hasCompositedLayerMapping()
         || !layer->compositedLayerMapping()->mainGraphicsLayer()) {
         // Don't raise exception in these cases which may be normally used in tests.
         return String();