Use gpu::Mailbox in IPCs instead of std::string

content/renderer/browser_plugin/browser_plugin_compositing_helper.h

Index: content/renderer/browser_plugin/browser_plugin_compositing_helper.h
diff --git a/content/renderer/browser_plugin/browser_plugin_compositing_helper.h b/content/renderer/browser_plugin/browser_plugin_compositing_helper.h
index 998b7397fa053a33d5f49ac1c0e9a9d6539c784c..8d9b1b2277fa2eafee5a365b714b344170d4da3c 100644
--- a/content/renderer/browser_plugin/browser_plugin_compositing_helper.h
+++ b/content/renderer/browser_plugin/browser_plugin_compositing_helper.h
@@ -17,6 +17,10 @@ class SolidColorLayer;
 class TextureLayer;
 }
 
+namespace gpu {
+struct Mailbox;
+}
+
 namespace WebKit {
 class WebPluginContainer;
 class WebLayer;
@@ -36,7 +40,7 @@ class CONTENT_EXPORT BrowserPluginCompositingHelper :
   void EnableCompositing(bool);
   void OnContainerDestroy();
   void OnBuffersSwapped(const gfx::Size& size,
-                        const std::string& mailbox_name,
+                        const gpu::Mailbox& mailbox_name,
                         int gpu_route_id,
                         int gpu_host_id,
                         float device_scale_factor);
@@ -46,9 +50,9 @@ class CONTENT_EXPORT BrowserPluginCompositingHelper :
   friend class base::RefCounted<BrowserPluginCompositingHelper>;
  private:
   ~BrowserPluginCompositingHelper();
-  void FreeMailboxMemory(const std::string& mailbox_name,
+  void FreeMailboxMemory(const gpu::Mailbox& mailbox_name,
                          unsigned sync_point);
-  void MailboxReleased(const std::string& mailbox_name,
+  void MailboxReleased(const gpu::Mailbox& mailbox_name,
                        int gpu_route_id,
                        int gpu_host_id,
                        unsigned sync_point);