Add support for MojoChannel field trial

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 <stddef.h>
 #include <stdint.h>
 #include <memory>
 #include <utility>
@@ skipping 181 matching lines @@
 #endif  // defined(OS_WIN)
   NOTREACHED();
   return MOJO_RESULT_UNKNOWN;
 }
 
 }  // namespace
 
 //------------------------------------------------------------------------------
 
 // static
-bool ChannelMojo::ShouldBeUsed() {
-  // TODO(rockot): Investigate performance bottlenecks and hopefully reenable
-  // this at some point. http://crbug.com/500019
-  return false;
-}
-
-// static
 scoped_ptr<ChannelMojo> ChannelMojo::Create(
     mojo::ScopedMessagePipeHandle handle,
     Mode mode,
     Listener* listener) {
   return make_scoped_ptr(new ChannelMojo(std::move(handle), mode, listener));
 }
 
 // static
 scoped_ptr<ChannelFactory> ChannelMojo::CreateServerFactory(
     mojo::ScopedMessagePipeHandle handle) {
@@ skipping 176 matching lines @@
     DCHECK(ok);
     if (!ok) {
       LOG(ERROR) << "Failed to add new Mojo handle.";
       return MOJO_RESULT_UNKNOWN;
     }
   }
   return MOJO_RESULT_OK;
 }
 
 }  // namespace IPC