Proper MouseEvent targeting. Adds a Window method that locates a Window for a given point.

aura/window_delegate.h

Index: aura/window_delegate.h
===================================================================
--- aura/window_delegate.h	(revision 98852)
+++ aura/window_delegate.h	(working copy)
@@ -12,12 +12,20 @@
 
 namespace aura {
 
+class MouseEvent;
+
 // Delegate interface for aura::Window.
 class WindowDelegate {
  public:
+  virtual bool OnMouseEvent(const MouseEvent& event) = 0;
+
   // Asks the delegate to paint window contents into the supplied canvas.
-   virtual void OnPaint(gfx::Canvas* canvas) = 0;
+  virtual void OnPaint(gfx::Canvas* canvas) = 0;
 
+  // Called when the Window has been destroyed (i.e. from its destructor).
+  // The delegate can use this as an opportunity to delete itself if necessary.
+  virtual void OnWindowDestroyed() = 0;
+
  protected:
   virtual ~WindowDelegate() {}
 };