make StackingClient dispatch to either ash or desktop

ui/views/widget/native_widget_aura.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 "ui/views/widget/native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/string_util.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/aura/client/activation_change_observer.h"
@@ skipping 104 matching lines @@
     gfx::NativeView parent = params.GetParent();
     if (parent && parent->type() != aura::client::WINDOW_TYPE_UNKNOWN) {
       parent->AddTransientChild(window_);
       parent = NULL;
     }
     // SetAlwaysOnTop before SetParent so that always-on-top container is used.
     SetAlwaysOnTop(params.keep_on_top);
     // If the parent is not specified, find the default parent for
     // the |window_| using the desired |window_bounds|.
     if (!parent) {
-      parent = aura::client::GetStackingClient(params.GetParent())->
-          GetDefaultParent(window_, window_bounds);
+      parent = aura::client::GetStackingClient()->
+          GetDefaultParent(params.context, window_, window_bounds);
     } else if (window_bounds == gfx::Rect()) {
       // If a parent is specified but no bounds are given,
       // use the origin of the parent's display so that the widget
       // will be added to the same display as the parent.
       gfx::Rect bounds = gfx::Screen::GetScreenFor(parent)->
           GetDisplayNearestWindow(parent).bounds();
       window_bounds.set_origin(bounds.origin());
     }
     window_->SetParent(parent);
   }
@@ skipping 865 matching lines @@
   return aura::Env::GetInstance()->is_mouse_button_down();
 }
 
 // static
 bool NativeWidgetPrivate::IsTouchDown() {
   return aura::Env::GetInstance()->is_touch_down();
 }
 
 }  // namespace internal
 }  // namespace views