[Aura] Turns on Window opacity support.

ui/aura/window.cc

 // Copyright (c) 2011 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/window.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "ui/aura/desktop.h"
@@ skipping 391 matching lines @@
     return IsVisible() && show_state_ == ui::SHOW_STATE_FULLSCREEN;
 
   for (Windows::const_iterator it = children_.begin();
        it != children_.end(); ++it) {
     if ((*it)->IsOrContainsFullscreenWindow())
       return true;
   }
   return false;
 }
 
+void Window::SetOpacity(unsigned char opacity) {
+  layer_->SetOpacity(opacity / 255.0);
+}
+
 // static
 ui::Animation* Window::CreateDefaultAnimation() {
   std::vector<ui::MultiAnimation::Part> parts;
   parts.push_back(ui::MultiAnimation::Part(200, ui::Tween::LINEAR));
   ui::MultiAnimation* multi_animation = new ui::MultiAnimation(parts);
   multi_animation->set_continuous(false);
   return multi_animation;
 }
 
 Desktop* Window::GetDesktop() {
@@ skipping 88 matching lines @@
 }
 
 void Window::OnPaintLayer(gfx::Canvas* canvas) {
   delegate_->OnPaint(canvas);
 }
 
 void Window::OnLayerAnimationEnded(const ui::Animation* animation) {
 }
 
 }  // namespace aura