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.h"
+
+#include "base/file_path.h"
+
+namespace {
+
+class AppListServiceDisabled : public AppListService {
+ public:
+  AppListServiceDisabled() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AppListServiceDisabled);
+};
+
+AppListServiceDisabled* GetDisabled() {
+  CR_DEFINE_STATIC_LOCAL(AppListServiceDisabled, disabled_instance, ());
+  return &disabled_instance;
+}
+
+}  // namespace
+
+// static
+AppListService* AppListService::Get() {
+  return GetDisabled();
+}
+
+// static
+base::FilePath AppListService::GetAppListProfilePath(
+    const base::FilePath& user_data_dir) {
+  NOTREACHED();
+  return base::FilePath();
+}
+
+// static
+void AppListService::RegisterAppListPrefs(PrefRegistrySimple* registry) {}