Make aura::clients take Window instead of RootWindow

ash/drag_drop/drag_drop_controller_unittest.cc

 // Copyright (c) 2012 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.
 
 #include "ash/drag_drop/drag_drop_controller.h"
 
 #include "ash/drag_drop/drag_drop_tracker.h"
 #include "ash/drag_drop/drag_image_view.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
@@ skipping 145 matching lines @@
   void Reset() {
     drag_start_received_ = false;
     num_drag_updates_ = 0;
     drop_received_ = false;
     drag_canceled_ = false;
     drag_string_.clear();
   }
 
   virtual int StartDragAndDrop(
       const ui::OSExchangeData& data,
-      aura::RootWindow* root_window,
+      aura::Window* root_window,
       aura::Window* source_window,
       const gfx::Point& location,
       int operation,
       ui::DragDropTypes::DragEventSource source) OVERRIDE {
     drag_start_received_ = true;
     data.GetString(&drag_string_);
     return DragDropController::StartDragAndDrop(
         data, root_window, source_window, location, operation, source);
   }
 
@@ skipping 922 matching lines @@
     EXPECT_EQ("405,405", observer.window_location_on_destroying().ToString());
   }
   for (Shell::RootWindowList::iterator iter = root_windows.begin();
        iter != root_windows.end(); ++iter) {
     aura::client::SetDragDropClient(*iter, NULL);
   }
 }
 
 }  // namespace test
 }  // namespace aura