Avoid using two-phase read with MOJO_READ_DATA_FLAG_ALL_OR_NONE.

mojo/services/network/public/cpp/web_socket_read_queue.h

 // Copyright 2014 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_SERVICES_NETWORK_PUBLIC_CPP_WEB_SOCKET_READ_QUEUE_H_
 #define MOJO_SERVICES_NETWORK_PUBLIC_CPP_WEB_SOCKET_READ_QUEUE_H_
 
 #include "base/callback.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
 #include "mojo/message_pump/handle_watcher.h"
 #include "third_party/mojo/src/mojo/public/cpp/system/data_pipe.h"
 
 namespace mojo {
 
 // This class simplifies the handling of multiple Reads on a DataPipe. It reads
 // the data in the expected chunk size, calling the callback once a full chunk
 // is ready. Callbacks are owned by this class, and are guaranteed not to be
 // called after this class is destroyed.
 // See also: WebSocketWriteQueue
 class WebSocketReadQueue {
  public:
   explicit WebSocketReadQueue(DataPipeConsumerHandle handle);
   ~WebSocketReadQueue();
 
-  void Read(uint32_t num_bytes, base::Callback<void(const char*)> callback);
+  void Read(uint32_t num_bytes,
+            const base::Callback<void(const char*)>& callback);
 
  private:
   struct Operation;
 
   void TryToRead();
   void Wait();
   void OnHandleReady(MojoResult result);
 
   DataPipeConsumerHandle handle_;
   common::HandleWatcher handle_watcher_;
   ScopedVector<Operation> queue_;
   bool is_busy_;
   base::WeakPtrFactory<WebSocketReadQueue> weak_factory_;
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_NETWORK_PUBLIC_CPP_WEB_SOCKET_READ_QUEUE_H_