Make cc::SurfaceId unguessable

content/browser/frame_host/cross_process_frame_connector.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_BROWSER_FRAME_HOST_CROSS_PROCESS_FRAME_CONNECTOR_H_
 #define CONTENT_BROWSER_FRAME_HOST_CROSS_PROCESS_FRAME_CONNECTOR_H_
 
 #include <stdint.h>
 
 #include "cc/output/compositor_frame.h"
 #include "content/browser/renderer_host/event_with_latency_info.h"
 #include "content/common/content_export.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace blink {
 class WebInputEvent;
 struct WebScreenInfo;
 }
 
 namespace cc {
-struct SurfaceId;
+class SurfaceId;
 struct SurfaceSequence;
 }
 
 namespace IPC {
 class Message;
 }
 
 namespace content {
 class RenderFrameProxyHost;
 class RenderWidgetHostImpl;
@@ skipping 109 matching lines @@
   RenderWidgetHostViewChildFrame* view_;
 
   gfx::Rect child_frame_rect_;
   float device_scale_factor_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_CROSS_PROCESS_FRAME_CONNECTOR_H_