aura: Unify WindowTreeHost for some platforms

ui/platform_window/stub/stub_window.cc

 // Copyright 2015 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 "ui/platform_window/stub/stub_window.h"
 
 #include "ui/platform_window/platform_window_delegate.h"
 
 namespace ui {
 
+// static
+scoped_ptr<PlatformWindow> PlatformWindow::Create(
+    PlatformWindowDelegate* delegate,
+    const gfx::Rect& bounds) {
+  return new StubWindow(delegate);
+}
+
 StubWindow::StubWindow(PlatformWindowDelegate* delegate) : delegate_(delegate) {
   delegate_->OnAcceleratedWidgetAvailable(gfx::kNullAcceleratedWidget, 1.f);
 }
 
 StubWindow::~StubWindow() {
 }
 
 void StubWindow::Show() {
 }
 
@@ skipping 42 matching lines @@
 }
 
 void StubWindow::ConfineCursorToBounds(const gfx::Rect& bounds) {
 }
 
 PlatformImeController* StubWindow::GetPlatformImeController() {
   return nullptr;
 }
 
 }  // namespace ui