aura: Draw drop shadows under browsers and menus.

ui/aura/window.h

Index: ui/aura/window.h
diff --git a/ui/aura/window.h b/ui/aura/window.h
index 6c53603f80886e945b110e7e6a3f1f7eb86bfe1d..7feae058ae61b7da5af0fbab31330d88f57b14fd 100644
--- a/ui/aura/window.h
+++ b/ui/aura/window.h
@@ -288,6 +288,12 @@ class AURA_EXPORT Window : public ui::LayerDelegate {
                             bool return_tightest,
                             bool for_event_handling);
 
+  // Called when this window's parent has changed.
+  void OnParentChanged();
+
+  // Called when this window's stacking order among its siblings is changed.
+  void OnStackingChanged();
+
   // Overridden from ui::LayerDelegate:
   virtual void OnPaintLayer(gfx::Canvas* canvas) OVERRIDE;