Make PlatformViewport and NativeViewportImpl use Shell* instead of ApplicationImpl*.

services/native_viewport/platform_viewport_stub.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 "services/native_viewport/platform_viewport_headless.h"
 
 namespace mojo {
 
 // static
-scoped_ptr<PlatformViewport> PlatformViewport::Create(
-    mojo::ApplicationImpl* application_,
-    Delegate* delegate) {
+scoped_ptr<PlatformViewport> PlatformViewport::Create(mojo::Shell* shell,
+                                                      Delegate* delegate) {
   return PlatformViewportHeadless::Create(delegate);
 }
 
 }  // namespace mojo