Don't call RenderObject::enclosingLayer on a null pointer

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index fb14b239c7a793aaa14b2e3d25578b73a064dfdc..ba8cca0f7d5d8ef99e1b655de4918b0e15d4b823 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -394,13 +394,15 @@ static void makeLayerChildFrameMap(const LocalFrame* currentFrame, LayerFrameMap
     map->clear();
     const FrameTree& tree = currentFrame->tree();
     for (const LocalFrame* child = tree.firstChild(); child; child = child->tree().nextSibling()) {
-        if (const RenderLayer* containingLayer = child->ownerRenderer()->enclosingLayer()) {
-            LayerFrameMap::iterator iter = map->find(containingLayer);
-            if (iter == map->end())
-                map->add(containingLayer, Vector<const LocalFrame*>()).storedValue->value.append(child);
-            else
-                iter->value.append(child);
-        }
+        const RenderObject* ownerRenderer = child->ownerRenderer();
+        if (!ownerRenderer)
+            continue;
+        const RenderLayer* containingLayer = ownerRenderer->enclosingLayer();
+        LayerFrameMap::iterator iter = map->find(containingLayer);
+        if (iter == map->end())
+            map->add(containingLayer, Vector<const LocalFrame*>()).storedValue->value.append(child);
+        else
+            iter->value.append(child);
     }
 }