Make cc::SurfaceId unguessable

content/renderer/render_frame_proxy.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 CONTENT_RENDERER_RENDER_FRAME_PROXY_H_
 #define CONTENT_RENDERER_RENDER_FRAME_PROXY_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "content/common/content_export.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_sender.h"
 #include "third_party/WebKit/public/platform/WebFocusType.h"
 #include "third_party/WebKit/public/web/WebRemoteFrame.h"
 #include "third_party/WebKit/public/web/WebRemoteFrameClient.h"
 #include "url/origin.h"
 
 struct FrameMsg_BuffersSwapped_Params;
 struct FrameMsg_CompositorFrameSwapped_Params;
 
 namespace blink {
 class WebInputEvent;
 struct WebRect;
 }
 
 namespace cc {
-struct SurfaceId;
+class SurfaceId;
 struct SurfaceSequence;
 }
 
 namespace content {
 
 class ChildFrameCompositingHelper;
 class RenderFrameImpl;
 class RenderViewImpl;
 class RenderWidget;
 struct ContentSecurityPolicyHeader;
@@ skipping 151 matching lines @@
 
   RenderViewImpl* render_view_;
   RenderWidget* render_widget_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameProxy);
 };
 
 }  // namespace
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_PROXY_H_