Second try for

ash/wm/window_util.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/wm/window_util.h"
 
 #include "ash/shell.h"
 #include "ash/wm/activation_controller.h"
 #include "ui/aura/client/activation_client.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_property.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/gfx/screen.h"
 
 DECLARE_WINDOW_PROPERTY_TYPE(bool);
 
 namespace ash {
 DEFINE_WINDOW_PROPERTY_KEY(bool, kOpenWindowSplitKey, false);
 
 namespace wm {
 
 void ActivateWindow(aura::Window* window) {
-  aura::client::GetActivationClient(Shell::GetRootWindow())->ActivateWindow(
+  DCHECK(window);
+  DCHECK(window->GetRootWindow());
+  aura::client::GetActivationClient(window->GetRootWindow())->ActivateWindow(
       window);
 }
 
 void DeactivateWindow(aura::Window* window) {
-  aura::client::GetActivationClient(Shell::GetRootWindow())->DeactivateWindow(
+  DCHECK(window);
+  DCHECK(window->GetRootWindow());
+  aura::client::GetActivationClient(window->GetRootWindow())->DeactivateWindow(
       window);
 }
 
 bool IsActiveWindow(aura::Window* window) {
-  return GetActiveWindow() == window;
+  DCHECK(window);
+  if (!window->GetRootWindow())
+    return false;
+
+  return aura::client::GetActivationClient(window->GetRootWindow())->
+      GetActiveWindow() == window;
 }
 
 aura::Window* GetActiveWindow() {
   return aura::client::GetActivationClient(Shell::GetRootWindow())->
       GetActiveWindow();
 }
 
 aura::Window* GetActivatableWindow(aura::Window* window) {
   return internal::ActivationController::GetActivatableWindow(window);
 }
@@ skipping 41 matching lines @@
 void SetOpenWindowSplit(aura::Window* window, bool value) {
   window->SetProperty(kOpenWindowSplitKey, value);
 }
 
 bool GetOpenWindowSplit(aura::Window* window) {
   return window->GetProperty(kOpenWindowSplitKey);
 }
 
 }  // namespace wm
 }  // namespace ash