Add GrabWindowSnapshotAsync tests

ui/aura/root_window_host_win.cc

 // Copyright (c) 2012 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/aura/root_window_host_win.h"
 
 #include <windows.h>
 
 #include <algorithm>
 
@@ skipping 34 matching lines @@
       saved_window_style_(0),
       saved_window_ex_style_(0) {
   if (use_popup_as_root_window_for_test)
     set_window_style(WS_POPUP);
   Init(NULL, bounds);
   SetWindowText(hwnd(), L"aura::RootWindow!");
   CreateCompositor(GetAcceleratedWidget());
 }
 
 WindowTreeHostWin::~WindowTreeHostWin() {
+  DestroyCompositor();
   DestroyWindow(hwnd());
 }
 
 RootWindow* WindowTreeHostWin::GetRootWindow() {
   return delegate_->AsRootWindow();
 }
 
 gfx::AcceleratedWidget WindowTreeHostWin::GetAcceleratedWidget() {
   return hwnd();
 }
@@ skipping 236 matching lines @@
 namespace test {
 
 // static
 void SetUsePopupAsRootWindowForTest(bool use) {
   use_popup_as_root_window_for_test = use;
 }
 
 }  // namespace test
 
 }  // namespace aura