Fix/reland 505555fa8031fc06d67e9ed43e3021d8d84cb44f (crrev.com/773983002).

mojo/edk/system/message_pipe.h

 // Copyright 2013 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 MOJO_EDK_SYSTEM_MESSAGE_PIPE_H_
 #define MOJO_EDK_SYSTEM_MESSAGE_PIPE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 89 matching lines @@
                       Channel* channel,
                       size_t* max_size,
                       size_t* max_platform_handles);
   bool EndSerialize(unsigned port,
                     Channel* channel,
                     void* destination,
                     size_t* actual_size,
                     embedder::PlatformHandleVector* platform_handles);
 
   // |ChannelEndpointClient| methods:
-  void OnReadMessage(unsigned port,
-                     scoped_ptr<MessageInTransit> message) override;
+  bool OnReadMessage(unsigned port, MessageInTransit* message) override;
   void OnDetachFromChannel(unsigned port) override;
 
  private:
   MessagePipe();
   virtual ~MessagePipe();
 
   // This is used internally by |WriteMessage()| and by |OnReadMessage()|.
   // |transports| may be non-null only if it's nonempty and |message| has no
-  // dispatchers attached.
-  MojoResult EnqueueMessage(unsigned port,
-                            scoped_ptr<MessageInTransit> message,
-                            std::vector<DispatcherTransport>* transports);
+  // dispatchers attached. Must be called with |lock_| held.
+  MojoResult EnqueueMessageNoLock(unsigned port,
+                                  scoped_ptr<MessageInTransit> message,
+                                  std::vector<DispatcherTransport>* transports);
 
-  // Helper for |EnqueueMessage()|. Must be called with |lock_| held.
+  // Helper for |EnqueueMessageNoLock()|. Must be called with |lock_| held.
   MojoResult AttachTransportsNoLock(
       unsigned port,
       MessageInTransit* message,
       std::vector<DispatcherTransport>* transports);
 
   base::Lock lock_;  // Protects the following members.
   scoped_ptr<MessagePipeEndpoint> endpoints_[2];
 
   DISALLOW_COPY_AND_ASSIGN(MessagePipe);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_MESSAGE_PIPE_H_