Attach panel while dragging to bring it in front of other panels.

ash/wm/gestures/two_finger_drag_handler.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/wm/gestures/two_finger_drag_handler.h"
 
 #include "ash/wm/window_resizer.h"
 #include "ash/wm/window_util.h"
 #include "ash/wm/workspace/snap_sizer.h"
 #include "ui/aura/client/window_types.h"
@@ skipping 80 matching lines @@
     return false;
   }
 
   if (event.type() == ui::ET_GESTURE_BEGIN &&
       event.details().touch_points() == 2) {
     if (!window_resizer_.get() && wm::IsWindowNormal(target) &&
       target->type() == aura::client::WINDOW_TYPE_NORMAL) {
       if (WindowComponentsAllowMoving(first_finger_hittest_,
           target->delegate()->GetNonClientComponent(event.location()))) {
         target->AddObserver(this);
-        window_resizer_ = CreateWindowResizer(target,
+        window_resizer_ = CreateWindowResizer(NULL, target,
             event.details().bounding_box().CenterPoint(), HTCAPTION);
         return true;
       }
     }
 
     return false;
   }
 
   if (!window_resizer_.get()) {
     // Consume all two-finger gestures on a normal window.
@@ skipping 74 matching lines @@
                                                      bool visible) {
   Reset();
 }
 
 void TwoFingerDragHandler::OnWindowDestroying(aura::Window* window) {
   Reset();
 }
 
 }  // namespace internal
 }  // namespace ash