Desktop aura: Break aura::Window::SetParent in two.

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 96 matching lines @@
     return 0;
 
   const ui::OSExchangeDataProviderAura& provider =
       static_cast<const ui::OSExchangeDataProviderAura&>(data.provider());
   // We do not support touch drag/drop without a drag image.
   if (source == ui::DragDropTypes::DRAG_EVENT_SOURCE_TOUCH &&
       provider.drag_image().size().IsEmpty())
     return 0;
 
   current_drag_event_source_ = source;
-  DragDropTracker* tracker = new DragDropTracker;
+  DragDropTracker* tracker = new DragDropTracker(root_window);
   if (source == ui::DragDropTypes::DRAG_EVENT_SOURCE_TOUCH) {
     // We need to transfer the current gesture sequence and the GR's touch event
     // queue to the |drag_drop_tracker_|'s capture window so that when it takes
     // capture, it still gets a valid gesture state.
     root_window->gesture_recognizer()->TransferEventsTo(source_window,
         tracker->capture_window());
     // We also send a gesture end to the source window so it can clear state.
     // TODO(varunjain): Remove this whole block when gesture sequence
     // transferring is properly done in the GR (http://crbug.com/160558)
     DispatchGestureEndToWindow(source_window);
@@ skipping 350 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