Move plugins to be stored in HTMLPlugInElement.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index a9d98d6c4e33a57f276cb1c0a0153326061ebce8..961486217260411a00f2e2e69167b480cd775b2f 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -148,11 +148,8 @@ static bool contentLayerSupportsDirectBackgroundComposition(
 static WebLayer* platformLayerForPlugin(LayoutObject& layoutObject) {
   if (!layoutObject.isEmbeddedObject())
     return nullptr;
-  FrameViewBase* frameViewBase =
-      toLayoutEmbeddedObject(layoutObject).frameViewBase();
-  if (!frameViewBase || !frameViewBase->isPluginView())
-    return nullptr;
-  return toPluginView(frameViewBase)->platformLayer();
+  PluginView* plugin = toLayoutEmbeddedObject(layoutObject).plugin();
+  return plugin ? plugin->platformLayer() : nullptr;
 }
 
 static inline bool isAcceleratedContents(LayoutObject& layoutObject) {