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

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::Window* CreateCaptureWindow(aura::RootWindow* context_root) {
   aura::Window* window = new aura::Window(NULL);
   window->SetType(aura::client::WINDOW_TYPE_NORMAL);
   window->Init(ui::LAYER_NOT_DRAWN);
-  window->SetParent(NULL);
+  window->SetDefaultParentByTargetRoot(context_root, gfx::Rect());
   window->Show();
   return window;
 }
 
 }  // namespace
 
 namespace ash {
 namespace internal {
 
-DragDropTracker::DragDropTracker()
-    : capture_window_(CreateCaptureWindow()) {
+DragDropTracker::DragDropTracker(aura::RootWindow* context_root)
+    : capture_window_(CreateCaptureWindow(context_root)) {
   capture_window_->SetCapture();
 }
 
 DragDropTracker::~DragDropTracker()  {
   capture_window_->ReleaseCapture();
 }
 
 aura::Window* DragDropTracker::GetTarget(const ui::LocatedEvent& event) {
   DCHECK(capture_window_.get());
   gfx::Point location_in_screen = event.location();
@@ skipping 21 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