First shot at implementing drag&drop for Aura

ui/aura/desktop.h

Index: ui/aura/desktop.h
diff --git a/ui/aura/desktop.h b/ui/aura/desktop.h
index 5f455ffccac0fd2bbf92c07d2c04a466b426c1ac..abbe126c6d16102543c531733de05a42c8152c0c 100644
--- a/ui/aura/desktop.h
+++ b/ui/aura/desktop.h
@@ -34,6 +34,7 @@ namespace aura {
 
 class DesktopHost;
 class DesktopObserver;
+class DragDropClient;
 class KeyEvent;
 class MouseEvent;
 class ScreenAura;
@@ -60,6 +61,7 @@ class AURA_EXPORT Desktop : public ui::CompositorDelegate,
   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_; }
@@ -67,6 +69,8 @@ class AURA_EXPORT Desktop : public ui::CompositorDelegate,
 
   void SetStackingClient(StackingClient* stacking_client);
 
+  void SetDragDropClient(DragDropClient* stacking_client);
+
   // Shows the desktop host.
   void ShowDesktop();
 
@@ -177,6 +181,8 @@ class AURA_EXPORT Desktop : public ui::CompositorDelegate,
 
   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