Add better handle tracking, and optimize Connector::Accept.

mojo/public/bindings/lib/message_queue.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/public/bindings/lib/message_queue.h"
 
 #include <assert.h>
 #include <stddef.h>
 
 #include "mojo/public/bindings/lib/message.h"
 
 namespace mojo {
 
 MessageQueue::MessageQueue() {
 }
 
 MessageQueue::~MessageQueue() {
   while (!queue_.empty())
     Pop();
 }
 
 bool MessageQueue::IsEmpty() const {
   return queue_.empty();
 }
 
-const Message* MessageQueue::Peek() const {
+Message* MessageQueue::Peek() {
   assert(!queue_.empty());
   return queue_.front();
 }
 
 void MessageQueue::Push(Message* message) {
   queue_.push(new Message());
   queue_.back()->Swap(message);
 }
 
 void MessageQueue::Pop(Message* message) {
   assert(!queue_.empty());
   queue_.front()->Swap(message);
   Pop();
 }
 
 void MessageQueue::Pop() {
   assert(!queue_.empty());
   delete queue_.front();
   queue_.pop();
 }
 
 }  // namespace mojo