Allow stacking below windows with layers with NULL delegates.

ui/aura/window_unittest.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/window.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 2153 matching lines @@
       CreateTestWindow(SK_ColorWHITE, 1, gfx::Rect(0, 0, 100, 100),
                        root_window()));
   scoped_ptr<ui::Layer>acquired_layer(w->AcquireLayer());
   scoped_ptr<ui::Layer>doubly_acquired_layer(w->RecreateLayer());
   EXPECT_EQ(NULL, doubly_acquired_layer.get());
 
   // Destroy window before layer gets destroyed.
   w.reset();
 }
 
+TEST_F(WindowTest, StackWindowAtBottomBelowWindowWhoseLayerHasNoDelegate) {
+  scoped_ptr<Window> window1(CreateTestWindowWithId(1, root_window()));
+  window1->layer()->set_name("1");
+  scoped_ptr<Window> window2(CreateTestWindowWithId(2, root_window()));
+  window2->layer()->set_name("2");
+  scoped_ptr<Window> window3(CreateTestWindowWithId(3, root_window()));
+  window3->layer()->set_name("3");
+
+  EXPECT_EQ("1 2 3", ChildWindowIDsAsString(root_window()));
+  EXPECT_EQ("1 2 3",
+            ui::test::ChildLayerNamesAsString(*root_window()->layer()));
+  window1->layer()->set_delegate(NULL);
+  root_window()->StackChildAtBottom(window3.get());
+
+  // Window 3 should have moved to the bottom.
+  EXPECT_EQ("3 1 2", ChildWindowIDsAsString(root_window()));
+  EXPECT_EQ("3 1 2",
+            ui::test::ChildLayerNamesAsString(*root_window()->layer()));
+}
+
 TEST_F(WindowTest, StackWindowsWhoseLayersHaveNoDelegate) {
   scoped_ptr<Window> window1(CreateTestWindowWithId(1, root_window()));
   window1->layer()->set_name("1");
   scoped_ptr<Window> window2(CreateTestWindowWithId(2, root_window()));
   window2->layer()->set_name("2");
   scoped_ptr<Window> window3(CreateTestWindowWithId(3, root_window()));
   window3->layer()->set_name("3");
 
   // This brings |window1| (and its layer) to the front.
   root_window()->StackChildAbove(window1.get(), window3.get());
@@ skipping 979 matching lines @@
   parent->AddTransientChild(transient);
   parent.reset();
 
   ASSERT_EQ(2u, destruction_order.size());
   EXPECT_EQ("transient", destruction_order[0]);
   EXPECT_EQ("parent", destruction_order[1]);
 }
 
 }  // namespace test
 }  // namespace aura