Make IPC::Channel::Listener:OnMessageReceived have a return value indicating whether a message was processed or not.

TBR=brettw
Review URL: http://codereview.chromium.org/5978003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@70139 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ppapi/proxy/ppp_class_proxy.h b/ppapi/proxy/ppp_class_proxy.h
index b22d86a04..d4e2102b 100644
--- a/ppapi/proxy/ppp_class_proxy.h
+++ b/ppapi/proxy/ppp_class_proxy.h
@@ -42,7 +42,7 @@
   // InterfaceProxy implementation.
   virtual const void* GetSourceInterface() const;
   virtual InterfaceID GetInterfaceId() const;
-  virtual void OnMessageReceived(const IPC::Message& msg);
+  virtual bool OnMessageReceived(const IPC::Message& msg);
 
  private:
   // IPC message handlers.