Rename the aura_shell namespace to ash

ash/drag_drop/drag_drop_controller.h

Index: ash/drag_drop/drag_drop_controller.h
===================================================================
--- ash/drag_drop/drag_drop_controller.h	(revision 115744)
+++ ash/drag_drop/drag_drop_controller.h	(working copy)
@@ -18,7 +18,7 @@
 class Window;
 }
 
-namespace aura_shell {
+namespace ash {
 
 namespace test {
 class DragDropControllerTest;
@@ -58,7 +58,7 @@
                                               aura::TouchEvent* event) OVERRIDE;
 
  private:
-  friend class aura_shell::test::DragDropControllerTest;
+  friend class ash::test::DragDropControllerTest;
 
   // Helper method to reset everything.
   void Cleanup();
@@ -78,6 +78,6 @@
 };
 
 }  // namespace internal
-}  // namespace aura_shell
+}  // namespace ash
 
 #endif  // ASH_DRAG_DROP_DRAG_DROP_CONTROLLER_H_