First shot at implementing drag&drop for Aura

ui/aura/desktop.h

 // 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.
 
 #ifndef UI_AURA_DESKTOP_H_
 #define UI_AURA_DESKTOP_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
@@ skipping 16 matching lines @@
 
 namespace ui {
 class LayerAnimationSequence;
 class Transform;
 }
 
 namespace aura {
 
 class DesktopHost;
 class DesktopObserver;
+class DragDropClient;
 class KeyEvent;
 class MouseEvent;
 class ScreenAura;
 class StackingClient;
 class TouchEvent;
 
 // Desktop is responsible for hosting a set of windows.
 class AURA_EXPORT Desktop : public ui::CompositorDelegate,
                             public Window,
                             public internal::FocusManager,
                             public ui::LayerAnimationObserver {
  public:
   Desktop();
   virtual ~Desktop();
 
   static Desktop* GetInstance();
   static void DeleteInstanceForTesting();
 
   static void set_use_fullscreen_host_window(bool use_fullscreen) {
     use_fullscreen_host_window_ = use_fullscreen;
   }
 
   ui::Compositor* compositor() { return compositor_.get(); }
   gfx::Point last_mouse_location() const { return last_mouse_location_; }
   gfx::NativeCursor last_cursor() const { return last_cursor_; }
   StackingClient* stacking_client() { return stacking_client_.get(); }
+  DragDropClient* drag_drop_client() { return drag_drop_client_.get(); }

[Ben Goodger (Google), 2011/11/11 17:26:53]

Since it looks like Desktop isn't actually using the client for anything itself,
I think DragDropClient should have its own GetInstance method so we don't need
to add this here.

[varunjain, 2011/11/15 19:39:33]

Done.

   Window* active_window() { return active_window_; }
   Window* mouse_pressed_handler() { return mouse_pressed_handler_; }
   Window* capture_window() { return capture_window_; }
   ScreenAura* screen() { return screen_; }
 
   void SetStackingClient(StackingClient* stacking_client);
 
+  void SetDragDropClient(DragDropClient* stacking_client);
+
   // Shows the desktop host.
   void ShowDesktop();
 
   // Sets the size of the desktop.
   void SetHostSize(const gfx::Size& size);
   gfx::Size GetHostSize() const;
 
   // Shows the specified cursor.
   void SetCursor(gfx::NativeCursor cursor);
 
@@ skipping 90 matching lines @@
   // Parses the switch describing the initial size for the host window and
   // returns bounds for the window.
   gfx::Rect GetInitialHostWindowBounds() const;
 
   scoped_refptr<ui::Compositor> compositor_;
 
   scoped_ptr<DesktopHost> host_;
 
   scoped_ptr<StackingClient> stacking_client_;
 
+  scoped_ptr<DragDropClient> drag_drop_client_;
+
   static Desktop* instance_;
 
   // If set before the Desktop is created, the host window will cover the entire
   // screen.  Note that this can still be overridden via the
   // switches::kAuraHostWindowSize flag.
   static bool use_fullscreen_host_window_;
 
   // Used to schedule painting.
   base::WeakPtrFactory<Desktop> schedule_paint_factory_;
 
@@ skipping 21 matching lines @@
   Window* mouse_moved_handler_;
   Window* focused_window_;
   Window* touch_event_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(Desktop);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_DESKTOP_H_