Support using TrackedCallbacks as hints to determine the handling thread of resource reply messages

ppapi/shared_impl/ppb_message_loop_shared.h

 // Copyright (c) 2012 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 PPAPI_SHARED_IMPL_PPB_MESSAGE_LOOP_SHARED_H_
 #define PPAPI_SHARED_IMPL_PPB_MESSAGE_LOOP_SHARED_H_
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/location.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/shared_impl/ppapi_shared_export.h"
 #include "ppapi/shared_impl/resource.h"
 #include "ppapi/thunk/ppb_message_loop_api.h"
 
+namespace base {
+class MessageLoopProxy;
+}
+
 namespace tracked_objects {
 class Location;
 }
 
 namespace ppapi {
 
 // MessageLoopShared doesn't really do anything interesting. It exists so that
 // shared code (in particular, TrackedCallback) can keep a pointer to a
 // MessageLoop resource. In the host side, there is not a concrete class that
 // implements this. So pointers to MessageLoopShared can only really be valid
@@ skipping 11 matching lines @@
 
   // Handles posting to the message loop if there is one, or the pending queue
   // if there isn't.
   // NOTE: The given closure will be run *WITHOUT* acquiring the Proxy lock.
   //       This only makes sense for user code and completely thread-safe
   //       proxy operations (e.g., MessageLoop::QuitClosure).
   virtual void PostClosure(const tracked_objects::Location& from_here,
                            const base::Closure& closure,
                            int64 delay_ms) = 0;
 
+  virtual base::MessageLoopProxy* GetMessageLoopProxy() = 0;
+
   DISALLOW_COPY_AND_ASSIGN(MessageLoopShared);
 };
 
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_PPB_MESSAGE_LOOP_SHARED_H_