Set DragDropTracker's capture window's size to zero, otherwise, it gets

ash/drag_drop/drag_drop_tracker.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_tracker.h"
 
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/coordinate_conversion.h"
 #include "ui/aura/root_window.h"
 #include "ui/base/events/event.h"
 #include "ui/gfx/screen.h"
 
 namespace {
 
 // Creates a window for capturing drag events.
 aura::Window* CreateCaptureWindow(aura::RootWindow* root_window) {
   aura::Window* window = new aura::Window(NULL);
   window->SetType(aura::client::WINDOW_TYPE_NORMAL);
   window->Init(ui::LAYER_NOT_DRAWN);
   window->SetParent(NULL);
-  window->SetBoundsInScreen(root_window->GetBoundsInScreen(),
+  window->SetBoundsInScreen(gfx::Rect(root_window->GetBoundsInScreen().origin(),
+                                      gfx::Size()),
                             gfx::Screen::GetDisplayNearestWindow(root_window));
   window->Show();
   return window;
 }
 
 }  // namespace
 
 namespace ash {
 namespace internal {
 
@@ skipping 33 matching lines @@
       ash::wm::GetRootWindowAt(location_in_screen),
       &target_root_location);
   return new ui::MouseEvent(event.type(),
                             target_location,
                             target_root_location,
                             event.flags());
 }
 
 }  // namespace internal
 }  // namespace ash