make StackingClient dispatch to either ash or desktop

content/shell/shell_stacking_client_ash.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 "content/shell/shell_stacking_client_ash.h"
 
 #include "ui/aura/client/default_capture_client.h"
 #include "ui/aura/focus_manager.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/shared/compound_event_filter.h"
 #include "ui/aura/shared/input_method_event_filter.h"
 #include "ui/aura/test/test_activation_client.h"
 
 namespace content {
 
 ShellStackingClientAsh::ShellStackingClientAsh() {
-  aura::client::SetStackingClient(this);
 }
 
 ShellStackingClientAsh::~ShellStackingClientAsh() {
   if (root_window_.get())
     root_window_event_filter_->RemoveFilter(input_method_filter_.get());
 
   aura::client::SetStackingClient(NULL);
 }
 
 aura::Window* ShellStackingClientAsh::GetDefaultParent(
+    aura::Window* context,
     aura::Window* window,
     const gfx::Rect& bounds) {
   if (!root_window_.get()) {
     aura::FocusManager* focus_manager = new aura::FocusManager;
 
     root_window_.reset(new aura::RootWindow(
         aura::RootWindow::CreateParams(gfx::Rect(100, 100))));
     root_window_->Init();
     root_window_->set_focus_manager(focus_manager);
 
     root_window_event_filter_ = new aura::shared::CompoundEventFilter;
     // Pass ownership of the filter to the root_window.
     root_window_->SetEventFilter(root_window_event_filter_);
 
     input_method_filter_.reset(new aura::shared::InputMethodEventFilter());
     input_method_filter_->SetInputMethodPropertyInRootWindow(
         root_window_.get());
     root_window_event_filter_->AddFilter(input_method_filter_.get());
 
     test_activation_client_.reset(
         new aura::test::TestActivationClient(root_window_.get()));
 
     capture_client_.reset(
         new aura::client::DefaultCaptureClient(root_window_.get()));
   }
   return root_window_.get();
 }
 
 }  // namespace content