V2 app support step2 : Use NativeAppWindow for Activity's window.

athena/test/sample_activity.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 "athena/test/sample_activity.h"
 
 #include "ui/views/background.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 
@@ skipping 55 matching lines @@
 
 views::View* SampleActivity::GetContentsView() {
   if (!contents_view_) {
     contents_view_ = new views::View;
     contents_view_->set_background(
         views::Background::CreateSolidBackground(contents_color_));
   }
   return contents_view_;
 }
 
+views::Widget* SampleActivity::CreateWidget() {
+  return NULL;
+}
+
 void SampleActivity::CreateOverviewModeImage() {
 }
 
 gfx::ImageSkia SampleActivity::GetOverviewModeImage() {
   return gfx::ImageSkia();
 }
 
 void SampleActivity::PrepareContentsForOverview() {
 }
 
 void SampleActivity::ResetContentsView() {
 }
 
 }  // namespace test
 }  // namespace athena