Mojo: Move platform handle/channel stuff in system to embedder namespace.

mojo/system/raw_channel_win.cc

 // Copyright 2013 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 "mojo/system/raw_channel.h"
 
 #include <stddef.h>
 
 #include "base/logging.h"
 
 namespace mojo {
 namespace system {
 
 // -----------------------------------------------------------------------------
 
 // Static factory method declared in raw_channel.h.
 // static
-RawChannel* RawChannel::Create(ScopedPlatformHandle handle,
+RawChannel* RawChannel::Create(embedder::ScopedPlatformHandle handle,
                                Delegate* delegate,
                                base::MessageLoop* message_loop) {
   // TODO(vtl)
   NOTIMPLEMENTED();
   return NULL;
 }
 
 }  // namespace system
 }  // namespace mojo