Revert 177182 - ViewTest.ChangeNativeViewHierarchyFindRoots failure

ui/aura/client/stacking_client.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/aura/client/stacking_client.h"
 
 #include "ui/aura/env.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window_property.h"
 
 DECLARE_WINDOW_PROPERTY_TYPE(aura::client::StackingClient*)
 
 namespace aura {
 namespace client {
 
 DEFINE_WINDOW_PROPERTY_KEY(
     StackingClient*, kRootWindowStackingClientKey, NULL);
 
+void SetStackingClient(StackingClient* stacking_client) {
+  Env::GetInstance()->set_stacking_client(stacking_client);
+}
+
+StackingClient* GetStackingClient() {
+  return Env::GetInstance()->stacking_client();
+}
+
 void SetStackingClient(Window* window, StackingClient* stacking_client) {
-  DCHECK(window);
-
-  RootWindow* root_window = window->GetRootWindow();
-  DCHECK(root_window);
-  root_window->SetProperty(kRootWindowStackingClientKey, stacking_client);
+  if (window) {
+    RootWindow* root_window = window->GetRootWindow();
+    DCHECK(root_window);
+    root_window->SetProperty(kRootWindowStackingClientKey, stacking_client);
+  } else {
+    SetStackingClient(stacking_client);
+  }
 }
 
 StackingClient* GetStackingClient(Window* window) {
-  DCHECK(window);
-  RootWindow* root_window = window->GetRootWindow();
-  DCHECK(root_window);
-  StackingClient* root_window_stacking_client =
-      root_window->GetProperty(kRootWindowStackingClientKey);
-  DCHECK(root_window_stacking_client);
-  return root_window_stacking_client;
+  if (window) {
+    RootWindow* root_window = window->GetRootWindow();
+    DCHECK(root_window);
+    StackingClient* root_window_stacking_client =
+        root_window->GetProperty(kRootWindowStackingClientKey);
+    if (root_window_stacking_client)
+      return root_window_stacking_client;
+  }
+  return GetStackingClient();
 }
 
 }  // namespace client
 }  // namespace aura