Remove remaining traces of WebCompositorImpl from the blink source.

Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 78 matching lines @@
 class MIDIClientProxy;
 class PinchViewports;
 class PrerendererClientImpl;
 class SharedWorkerRepositoryClientImpl;
 class SpeechInputClientImpl;
 class SpeechRecognitionClientProxy;
 class UserMediaClientImpl;
 class ValidationMessageClientImpl;
 class WebAXObject;
 class WebActiveGestureAnimation;
-class WebCompositorImpl;
 class WebDevToolsAgentClient;
 class WebDevToolsAgentPrivate;
 class WebDocument;
 class WebFrameImpl;
 class WebGestureEvent;
 class WebHelperPluginImpl;
 class WebImage;
 class WebKeyboardEvent;
 class WebLayerTreeView;
 class WebMouseEvent;
@@ skipping 718 matching lines @@
 inline WebViewImpl* toWebViewImpl(WebView* webView)
 {
     // We have no ways to check if the specified WebView is an instance of
     // WebViewImpl because WebViewImpl is the only implementation of WebView.
     return static_cast<WebViewImpl*>(webView);
 }
 
 } // namespace blink
 
 #endif