Reland of Use a token to initialise ChannelMojo and MojoApplication everywhere.

content/common/mojo/channel_init.h

-// Copyright 2015 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 CONTENT_COMMON_MOJO_CHANNEL_INIT_H_
-#define CONTENT_COMMON_MOJO_CHANNEL_INIT_H_
-
-#include "base/files/file.h"
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "content/common/content_export.h"
-#include "mojo/public/cpp/system/message_pipe.h"
-
-namespace base {
-class TaskRunner;
-}
-
-namespace content {
-
-// ChannelInit handles creation and destruction of the Mojo channel. It is not
-// thread-safe, but may be used on any single thread with a MessageLoop.
-//
-// TODO(rockot): Get rid of this class ASAP (i.e. once the patch which includes
-// this TODO has stuck for a bit) since it's no longer necessary.
-class CONTENT_EXPORT ChannelInit {
- public:
-  ChannelInit();
-  ~ChannelInit();
-
-  // Initializes the channel. This takes ownership of |file|.
-  mojo::ScopedMessagePipeHandle Init(
-      base::PlatformFile file,
-      scoped_refptr<base::TaskRunner> io_thread_task_runner);
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(ChannelInit);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_COMMON_MOJO_CHANNEL_INIT_H_