aura: No shadow for transparent window.

ui/aura/window.h

 // 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.
 
 #ifndef UI_AURA_WINDOW_H_
 #define UI_AURA_WINDOW_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 52 matching lines @@
 
   int id() const { return id_; }
   void set_id(int id) { id_ = id; }
 
   const std::string& name() const { return name_; }
   void SetName(const std::string& name);
 
   const string16 title() const { return title_; }
   void set_title(const string16& title) { title_ = title; }
 
+  bool transparent() const { return transparent_; }
+  void SetTransparent(bool transparent);
+
   ui::Layer* layer() { return layer_.get(); }
   const ui::Layer* layer() const { return layer_.get(); }
 
   // Releases the Window's reference to its layer, and returns it.
   // This is used when you need to animate the presentation of the Window just
   // prior to destroying it. The window can be destroyed soon after calling this
   // function, and the caller is then responsible for disposing of the layer
   // once any animation completes.
   // Note that Window methods generally don't expect a NULL layer, and so this
   // function should only be called right before destroying the Window,
@@ skipping 251 matching lines @@
   // Transient windows.
   Windows transient_children_;
 
   Window* transient_parent_;
 
   int id_;
   std::string name_;
 
   string16 title_;
 
+  // Whether layer is initialized as non-opaque.
+  bool transparent_;
+
   scoped_ptr<EventFilter> event_filter_;
   scoped_ptr<LayoutManager> layout_manager_;
 
   void* user_data_;
 
   // When true, events are not sent to windows behind this one in the z-order,
   // provided this window has children. See set_stops_event_propagation().
   bool stops_event_propagation_;
 
   // Makes the window pass all events through to any windows behind it.
   bool ignore_events_;
 
   ObserverList<WindowObserver> observers_;
 
   // We're using ViewProp to store the property (for now) instead of
   // just using std::map because chrome is still using |ViewProp| class
   // to create and access property.
   // TODO(oshima): Consolidcate ViewProp and aura::window property
   // implementation.
   std::map<const char*, void*> prop_map_;
 
   DISALLOW_COPY_AND_ASSIGN(Window);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_H_