Remove RootWindow reference from DragDropTracker. RootWindow reference in

ash/drag_drop/drag_drop_controller.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/wm/coordinate_conversion.h"
@@ skipping 44 matching lines @@
   if (drag_image_.get())
     drag_image_.reset();
 }
 
 int DragDropController::StartDragAndDrop(const ui::OSExchangeData& data,
                                          aura::RootWindow* root_window,
                                          const gfx::Point& root_location,
                                          int operation) {
   DCHECK(!IsDragDropInProgress());
 
-  drag_drop_tracker_.reset(new DragDropTracker(root_window));
+  drag_drop_tracker_.reset(new DragDropTracker);
 
   drag_data_ = &data;
   drag_operation_ = operation;
   const ui::OSExchangeDataProviderAura& provider =
       static_cast<const ui::OSExchangeDataProviderAura&>(data.provider());
 
   drag_image_.reset(new DragImageView);
   drag_image_->SetImage(provider.drag_image());
   drag_image_offset_ = provider.drag_image_offset();
   drag_image_->SetBoundsInScreen(gfx::Rect(
@@ skipping 222 matching lines @@
     drag_window_->RemoveObserver(this);
   drag_window_ = NULL;
   drag_data_ = NULL;
   // Cleanup can be called again while deleting DragDropTracker, so use Pass
   // instead of reset to avoid double free.
   drag_drop_tracker_.Pass();
 }
 
 }  // namespace internal
 }  // namespace ash