Introduce a couple of abstract bases for WebDataService.

chrome/browser/api/webdata/web_data_service_base.cc

Index: chrome/browser/api/webdata/web_data_service_base.cc
diff --git a/chrome/browser/api/webdata/web_data_service_base.cc b/chrome/browser/api/webdata/web_data_service_base.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5284e508c8d9a10a45b113b62511f0a4ba7dc241
--- /dev/null
+++ b/chrome/browser/api/webdata/web_data_service_base.cc
@@ -0,0 +1,11 @@
+// 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 "chrome/browser/api/webdata/web_data_service_base.h"
+
+#include "content/public/browser/browser_thread.h"
+
+WebDataServiceBase::WebDataServiceBase()
+    : RefcountedProfileKeyedService(content::BrowserThread::UI) {
+}