[Aura] Support always-on-top top level window.

ui/aura_shell/stacking_controller.cc

 // Copyright (c) 2011 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/aura_shell/stacking_controller.h"
 
 #include "ui/aura/desktop.h"
 #include "ui/aura/window.h"
+#include "ui/aura_shell/always_on_top_controller.h"
 #include "ui/aura_shell/shell.h"
 #include "ui/aura_shell/shell_window_ids.h"
 
 namespace aura_shell {
 namespace internal {
 namespace {
 
 aura::Window* GetContainer(int id) {
   return Shell::GetInstance()->GetContainer(id);
 }
 
 // Returns true if children of |window| can be activated.
 bool SupportsChildActivation(aura::Window* window) {
   return window->id() == kShellWindowId_DefaultContainer ||
          window->id() == kShellWindowId_AlwaysOnTopContainer;
 }
 
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // StackingController, public:
 
 StackingController::StackingController() {
   aura::Desktop::GetInstance()->SetStackingClient(this);
 }
 
 StackingController::~StackingController() {
 }
 
+void StackingController::Init() {
+  always_on_top_controller_.reset(new internal::AlwaysOnTopController);
+  always_on_top_controller_->SetContainers(
+      GetContainer(internal::kShellWindowId_DefaultContainer),
+      GetContainer(internal::kShellWindowId_AlwaysOnTopContainer));
+}
+
 // static
 aura::Window* StackingController::GetActivatableWindow(aura::Window* window) {
   aura::Window* parent = window->parent();
   aura::Window* child = window;
   while (parent) {
     if (SupportsChildActivation(parent))
       return child;
     // If |child| isn't activatable, but has transient parent, trace
     // that path instead.
     if (child->transient_parent())
       return GetActivatableWindow(child->transient_parent());
     parent = parent->parent();
     child = child->parent();
   }
   return NULL;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // StackingController, aura::StackingClient implementation:
 
 void StackingController::AddChildToDefaultParent(aura::Window* window) {
   aura::Window* parent = NULL;
   switch (window->type()) {
     case aura::WINDOW_TYPE_NORMAL:
     case aura::WINDOW_TYPE_POPUP:
-      parent = GetContainer(internal::kShellWindowId_DefaultContainer);
+      parent = always_on_top_controller_->GetContainer(window);
       break;
     case aura::WINDOW_TYPE_MENU:
     case aura::WINDOW_TYPE_TOOLTIP:
       parent = GetContainer(internal::kShellWindowId_MenusAndTooltipsContainer);
       break;
     default:
       NOTREACHED() << "Window " << window->id()
                    << " has unhandled type " << window->type();
       break;
   }
@@ skipping 16 matching lines @@
   }
   return NULL;
 }
 
 
 ////////////////////////////////////////////////////////////////////////////////
 // StackingController, private:
 
 }  // namespace internal
 }  // namespace aura_shell