Refactor app_list_util.h into AppListService abstract base.

chrome/browser/ui/app_list/app_list_service_disabled.cc

+// Copyright 2013 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 "chrome/browser/ui/app_list/app_list_service_disabled.h"
+
+#include "base/files/file_path.h"
+#include "base/memory/singleton.h"
+#include "chrome/browser/ui/app_list/app_list_service.h"
+
+namespace {
+
+class AppListServiceDisabled : public AppListService {
+ public:
+  static AppListServiceDisabled* GetInstance() {
+    return Singleton<AppListServiceDisabled,
+                     LeakySingletonTraits<AppListServiceDisabled> >::get();
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<AppListServiceDisabled>;
+
+  AppListServiceDisabled() {}
+
+  DISALLOW_COPY_AND_ASSIGN(AppListServiceDisabled);
+};
+
+}  // namespace
+
+namespace chrome {
+
+AppListService* GetAppListServiceDisabled() {
+  return AppListServiceDisabled::GetInstance();
+}
+
+}  // namespace chrome