Mojo: Dispatcher::MessageInTransitAccess functions don't need to take the lock.

mojo/system/message_pipe_dispatcher.cc

 // 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.
 
 #include "mojo/system/message_pipe_dispatcher.h"
 
 #include "base/logging.h"
 #include "mojo/system/channel.h"
 #include "mojo/system/constants.h"
 #include "mojo/system/local_message_pipe_endpoint.h"
@@ skipping 156 matching lines @@
   return message_pipe_->AddWaiter(port_, waiter, flags, wake_result);
 }
 
 void MessagePipeDispatcher::RemoveWaiterImplNoLock(Waiter* waiter) {
   lock().AssertAcquired();
   message_pipe_->RemoveWaiter(port_, waiter);
 }
 
 size_t MessagePipeDispatcher::GetMaximumSerializedSizeImplNoLock(
     const Channel* /*channel*/) const {
-  lock().AssertAcquired();
+  DCHECK(HasOneRef());  // Only one ref => no need to take the lock.
   return sizeof(SerializedMessagePipeDispatcher);
 }
 
 bool MessagePipeDispatcher::SerializeAndCloseImplNoLock(Channel* channel,
                                                         void* destination,
                                                         size_t* actual_size) {
-  lock().AssertAcquired();
+  DCHECK(HasOneRef());  // Only one ref => no need to take the lock.
 
   // Convert the local endpoint to a proxy endpoint (moving the message queue).
   message_pipe_->ConvertLocalToProxy(port_);
 
   // Attach the new proxy endpoint to the channel.
   MessageInTransit::EndpointId endpoint_id =
       channel->AttachMessagePipeEndpoint(message_pipe_, port_);
   DCHECK_NE(endpoint_id, MessageInTransit::kInvalidEndpointId);
 
   DVLOG(2) << "Serializing message pipe dispatcher (local ID = " << endpoint_id
@@ skipping 13 matching lines @@
 
 // MessagePipeDispatcherTransport ----------------------------------------------
 
 MessagePipeDispatcherTransport::MessagePipeDispatcherTransport(
     DispatcherTransport transport) : DispatcherTransport(transport) {
   DCHECK_EQ(message_pipe_dispatcher()->GetType(), Dispatcher::kTypeMessagePipe);
 }
 
 }  // namespace system
 }  // namespace mojo