Add compile flag for enabling the compostior

sky/engine/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 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 166 matching lines @@
     pageClients.editorClient = &m_editorClientImpl;
     pageClients.spellCheckerClient = &m_spellCheckerClientImpl;
 
     m_page = adoptPtr(new Page(pageClients, m_client->services()));
     m_page->makeOrdinary();
 
     setDeviceScaleFactor(m_client->screenInfo().deviceScaleFactor);
     setVisibilityState(m_client->visibilityState(), true);
 
     m_layerTreeView = m_client->initializeLayerTreeView();
+
+#if !ENABLE(COMPOSITOR)
+    m_layerTreeView = nullptr;
+#endif
 }
 
 WebViewImpl::~WebViewImpl()
 {
     ASSERT(!m_page);
 }
 
 WebLocalFrameImpl* WebViewImpl::mainFrameImpl()
 {
     return m_page ? WebLocalFrameImpl::fromFrame(m_page->mainFrame()) : 0;
@@ skipping 2062 matching lines @@
         m_layerTreeView->setVisible(visible);
     }
 }
 
 bool WebViewImpl::shouldDisableDesktopWorkarounds()
 {
     return true;
 }
 
 } // namespace blink