Use a boolean hasCompositedLayerMapping() accessor instead of the pointer

Source/core/inspector/InspectorLayerTreeAgent.cpp

Index: Source/core/inspector/InspectorLayerTreeAgent.cpp
diff --git a/Source/core/inspector/InspectorLayerTreeAgent.cpp b/Source/core/inspector/InspectorLayerTreeAgent.cpp
index 1d56a28c3ec98b72066f643086df81a947df14ac..88e266bb27fbb63b02c268f6ede22269235e71c9 100644
--- a/Source/core/inspector/InspectorLayerTreeAgent.cpp
+++ b/Source/core/inspector/InspectorLayerTreeAgent.cpp
@@ -152,11 +152,10 @@ void InspectorLayerTreeAgent::layerTreeDidChange()
 void InspectorLayerTreeAgent::didPaint(RenderObject* renderer, GraphicsContext*, const LayoutRect& rect)
 {
     RenderLayer* renderLayer = toRenderLayerModelObject(renderer)->layer();
-    CompositedLayerMapping* compositedLayerMapping = renderLayer->compositedLayerMapping();
     // Should only happen for FrameView paints when compositing is off. Consider different instrumentation method for that.
-    if (!compositedLayerMapping)
+    if (!renderLayer->hasCompositedLayerMapping())
         return;
-    GraphicsLayer* graphicsLayer = compositedLayerMapping->mainGraphicsLayer();
+    GraphicsLayer* graphicsLayer = renderLayer->compositedLayerMapping()->mainGraphicsLayer();
     RefPtr<TypeBuilder::DOM::Rect> domRect = TypeBuilder::DOM::Rect::create()
         .setX(rect.x())
         .setY(rect.y())
@@ -179,7 +178,7 @@ PassRefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> > InspectorLayerTre
 
 void InspectorLayerTreeAgent::buildLayerIdToNodeIdMap(RenderLayer* root, LayerIdToNodeIdMap& layerIdToNodeIdMap)
 {
-    if (root->compositedLayerMapping()) {
+    if (root->hasCompositedLayerMapping()) {
         if (Node* node = root->renderer()->generatingNode()) {
             GraphicsLayer* graphicsLayer = root->compositedLayerMapping()->childForSuperlayers();
             layerIdToNodeIdMap.set(graphicsLayer->platformLayer()->id(), idForNode(node));