ChannelMojo: Add ChannelMojo::CanBeUsed() to enable it incrementally

ipc/mojo/ipc_channel_mojo.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 IPC_IPC_CHANNEL_MOJO_H_
 #define IPC_IPC_CHANNEL_MOJO_H_
 
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 49 matching lines @@
                                     public MojoBootstrap::Delegate {
  public:
   class Delegate {
    public:
     virtual ~Delegate() {}
     virtual base::WeakPtr<Delegate> ToWeakPtr() = 0;
     virtual scoped_refptr<base::TaskRunner> GetIOTaskRunner() = 0;
     virtual void OnChannelCreated(base::WeakPtr<ChannelMojo> channel) = 0;
   };
 
+  // True if ChannelMojo should be used regardless of the flag.
+  static bool ShouldBeUsed();
+
   // Create ChannelMojo. A bootstrap channel is created as well.
   // |host| must not be null for server channels.
   static scoped_ptr<ChannelMojo> Create(Delegate* delegate,
                                         const ChannelHandle& channel_handle,
                                         Mode mode,
                                         Listener* listener);
 
   // Create a factory object for ChannelMojo.
   // The factory is used to create Mojo-based ChannelProxy family.
   // |host| must not be null.
@@ skipping 74 matching lines @@
   ScopedVector<Message> pending_messages_;
 
   base::WeakPtrFactory<ChannelMojo> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChannelMojo);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_MOJO_H_