Fix ThreadSafeAssociatedInterfacePtrProvider raciness.

ipc/ipc_channel_proxy.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 IPC_IPC_CHANNEL_PROXY_H_
 #define IPC_IPC_CHANNEL_PROXY_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 224 matching lines @@
   // Creates an AssociatedInterfacePtr to |Interface| on the IO thread and
   // passes it to |callback|, also invoked on the IO thread.
   template <typename Interface>
   void RetrieveAssociatedInterfaceOnIOThread(
       const AssociatedInterfaceRetrievedCallback<Interface>& callback) {
     context_->ipc_task_runner()->PostTask(
         FROM_HERE, base::Bind(&Context::RetrieveAssociatedInterface<Interface>,
                               context_, callback));
   }
 
+  base::SingleThreadTaskRunner* ipc_task_runner() const {
+    return context_->ipc_task_runner();
+  }
+
   // Called to clear the pointer to the IPC task runner when it's going away.
   void ClearIPCTaskRunner();
 
  protected:
   class Context;
   // A subclass uses this constructor if it needs to add more information
   // to the internal state.
   explicit ChannelProxy(Context* context);
 
   // Used internally to hold state that is referenced on the IPC thread.
@@ skipping 167 matching lines @@
   bool did_init_;
 
 #if defined(ENABLE_IPC_FUZZER)
   OutgoingMessageFilter* outgoing_message_filter_;
 #endif
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_PROXY_H_