Remove more bits of the Oilpan tracing system

sky/engine/core/frame/FrameHost.h

 /*
  * Copyright (C) 2013 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 26 matching lines @@
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class Chrome;
 class Page;
 class ServiceProvider;
 class Settings;
 class UseCounter;
-class Visitor;
 
 // FrameHost is the set of global data shared between multiple frames
 // and is provided by the embedder to each frame when created.
 // FrameHost currently corresponds to the Page object in core/page
 // however the concept of a Page is moving up out of Blink.
 // In an out-of-process iframe world, a single Page may have
 // multiple frames in different process, thus Page becomes a
 // browser-level concept and Blink core/ only knows about its LocalFrame (and FrameHost).
 // Separating Page from the rest of core/ through this indirection
 // allows us to slowly refactor Page without breaking the rest of core.
@@ skipping 19 matching lines @@
 private:
     FrameHost(Page&, ServiceProvider&);
 
     Page* m_page;
     ServiceProvider& m_services;
 };
 
 }
 
 #endif // FrameHost_h