Allow Alt-Tab to move the focus to docked windows.

ash/accelerators/accelerator_controller_unittest.cc

Index: ash/accelerators/accelerator_controller_unittest.cc
diff --git a/ash/accelerators/accelerator_controller_unittest.cc b/ash/accelerators/accelerator_controller_unittest.cc
index de0f057ba96363599111cc64d945a1a8ab5e6bdd..1d731b3c4f3fc92831b0c20174e0ff120fcb8d2a 100644
--- a/ash/accelerators/accelerator_controller_unittest.cc
+++ b/ash/accelerators/accelerator_controller_unittest.cc
@@ -653,9 +653,10 @@ TEST_F(AcceleratorControllerTest, CenterWindowAccelerator) {
 
   // Add the window to docked container and try to center it.
   window->SetBounds(gfx::Rect(0, 0, 20, 20));
-  aura::Window* docked_container = Shell::GetContainer(
-      window->GetRootWindow(), kShellWindowId_DockedContainer);
-  docked_container->AddChild(window.get());
+  const wm::WMEvent event(wm::WM_EVENT_DOCK);
+  wm::GetWindowState(window.get())->OnWMEvent(&event);
+  EXPECT_EQ(kShellWindowId_DockedContainer, window->parent()->id());
+
   gfx::Rect docked_bounds = window->GetBoundsInScreen();
   GetController()->PerformActionIfEnabled(WINDOW_POSITION_CENTER);
   // It should not get centered and should remain docked.