Enable the FocusController on DesktopAura too.

ui/views/widget/desktop_aura/desktop_focus_rules.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/views/widget/desktop_aura/desktop_focus_rules.h"
+
+#include "ui/aura/root_window.h"
+#include "ui/aura/window.h"
+
+namespace views {
+
+DesktopFocusRules::DesktopFocusRules() {}
+DesktopFocusRules::~DesktopFocusRules() {}
+
+bool DesktopFocusRules::SupportsChildActivation(aura::Window* window) const {
+  // In Desktop-Aura, only children of the RootWindow are activatable.
+  return window->GetRootWindow() == window;
+}
+
+}  // namespace views