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

ipc/mojo/ipc_channel_mojo.cc

 // 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.
 
 #include "ipc/mojo/ipc_channel_mojo.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/lazy_instance.h"
 #include "ipc/ipc_listener.h"
@@ skipping 35 matching lines @@
 //------------------------------------------------------------------------------
 
 void ChannelMojo::ChannelInfoDeleter::operator()(
     mojo::embedder::ChannelInfo* ptr) const {
   mojo::embedder::DestroyChannelOnIOThread(ptr);
 }
 
 //------------------------------------------------------------------------------
 
 // static
+bool ChannelMojo::ShouldBeUsed() {
+  // TODO(morrita): Turn this on for a set of platforms.
+  return false;
+}
+
+// static
 scoped_ptr<ChannelMojo> ChannelMojo::Create(ChannelMojo::Delegate* delegate,
                                             const ChannelHandle& channel_handle,
                                             Mode mode,
                                             Listener* listener) {
   return make_scoped_ptr(
       new ChannelMojo(delegate, channel_handle, mode, listener));
 }
 
 // static
 scoped_ptr<ChannelFactory> ChannelMojo::CreateServerFactory(
@@ skipping 209 matching lines @@
 
     fdset->CommitAll();
   }
 
   return MOJO_RESULT_OK;
 }
 
 #endif  // defined(OS_POSIX) && !defined(OS_NACL)
 
 }  // namespace IPC