athena: Remove ActivityViewModel::CreateWidget().

athena/test/base/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/base/sample_activity.h"
 
 #include "athena/input/public/accelerator_manager.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/views/background.h"
 #include "ui/views/view.h"
@@ skipping 67 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 nullptr;
-}
-
 gfx::ImageSkia SampleActivity::GetOverviewModeImage() {
   return gfx::ImageSkia();
 }
 
 void SampleActivity::PrepareContentsForOverview() {
 }
 
 void SampleActivity::ResetContentsView() {
 }
 
 }  // namespace test
 }  // namespace athena