Oilpan: extend tracing over WebFrame trees.

Source/web/WebRemoteFrameImpl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebRemoteFrameImpl_h
 #define WebRemoteFrameImpl_h
 
 #include "platform/heap/Handle.h"
 #include "public/web/WebRemoteFrame.h"
 #include "public/web/WebRemoteFrameClient.h"
@@ skipping 166 matching lines @@
 
     void setCoreFrame(PassRefPtrWillBeRawPtr<RemoteFrame>);
     RemoteFrame* frame() const { return m_frame.get(); }
 
     WebRemoteFrameClient* client() const { return m_client; }
 
     static WebRemoteFrameImpl* fromFrame(RemoteFrame&);
 
     virtual void initializeFromFrame(WebLocalFrame*) const OVERRIDE;
 
-    virtual void trace(Visitor*);
+#if ENABLE(OILPAN)
+    void trace(Visitor*);
+#endif
 
 private:
     RemoteFrameClientImpl m_frameClient;
     RefPtrWillBeMember<RemoteFrame> m_frame;
     WebRemoteFrameClient* m_client;
 
     WillBeHeapHashMap<WebFrame*, OwnPtrWillBeMember<FrameOwner> > m_ownersForChildren;
 
 #if ENABLE(OILPAN)
     // Oilpan: to provide the guarantee of having the frame live until
     // close() is called, an instance keep a self-persistent. It is
     // cleared upon calling close(). This avoids having to assume that
     // an embedder's WebFrame references are all discovered via thread
     // state (stack, registers) should an Oilpan GC strike while we're
     // in the process of detaching.
     GC_PLUGIN_IGNORE("340522")
     Persistent<WebRemoteFrameImpl> m_selfKeepAlive;
 #endif
 };
 
 DEFINE_TYPE_CASTS(WebRemoteFrameImpl, WebFrame, frame, frame->isWebRemoteFrame(), frame.isWebRemoteFrame());
 
 } // namespace blink
 
 #endif // WebRemoteFrameImpl_h