Separate athena's startup process from AppShell's

extensions/shell/browser/desktop_controller.cc

+// Copyright 2014 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 "extensions/shell/browser/desktop_controller.h"
+
+#include "base/logging.h"
+#include "base/macros.h"
+
+namespace extensions {
+namespace {
+
+DesktopController* g_instance = NULL;
+
+}  // namespace
+
+// static
+DesktopController* DesktopController::instance() {
+  return g_instance;
+}
+
+DesktopController::DesktopController() {
+  CHECK(!g_instance) << "DesktopController already exists";
+  g_instance = this;
+}
+
+DesktopController::~DesktopController() {
+  DCHECK(g_instance);
+  g_instance = NULL;
+}
+
+}  // namespace extensions