Move the concept of Activation to the Shell.

ui/aura_shell/modal_container_layout_manager.cc

Index: ui/aura_shell/modal_container_layout_manager.cc
===================================================================
--- ui/aura_shell/modal_container_layout_manager.cc	(revision 114022)
+++ ui/aura_shell/modal_container_layout_manager.cc	(working copy)
@@ -11,7 +11,7 @@
 #include "ui/aura/window.h"
 #include "ui/aura_shell/modality_event_filter.h"
 #include "ui/aura_shell/shell.h"
-#include "ui/aura_shell/stacking_controller.h"
+#include "ui/aura_shell/window_util.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/compositor/layer.h"
 #include "ui/gfx/compositor/layer_animator.h"
@@ -126,7 +126,7 @@
 
 bool ModalContainerLayoutManager::CanWindowReceiveEvents(
     aura::Window* window) {
-  return StackingController::GetActivatableWindow(window) == modal_window();
+  return GetActivatableWindow(window) == modal_window();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -135,8 +135,6 @@
 void ModalContainerLayoutManager::AddModalWindow(aura::Window* window) {
   modal_windows_.push_back(window);
   CreateModalScreen();
-  container_->StackChildAtTop(window);
-  window->Activate();
 }
 
 void ModalContainerLayoutManager::RemoveModalWindow(aura::Window* window) {
@@ -148,7 +146,7 @@
   if (modal_windows_.empty())
     HideModalScreen();
   else
-    modal_window()->Activate();
+    aura_shell::ActivateWindow(modal_window());
 }
 
 void ModalContainerLayoutManager::CreateModalScreen() {