Introduce a couple of abstract bases for WebDataService.

chrome/browser/api/webdata/autofill_web_data_service.h

+// 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.
+
+#ifndef CHROME_BROWSER_API_WEBDATA_AUTOFILL_WEB_DATA_SERVICE_H_
+#define CHROME_BROWSER_API_WEBDATA_AUTOFILL_WEB_DATA_SERVICE_H_
+
+#include "chrome/browser/api/webdata/autofill_web_data.h"
+
+namespace content {
+class BrowserContext;
+}
+
+// API for Autofill web data.
+class AutofillWebDataService
+    : public AutofillWebData,
+      public WebDataServiceBase {
+ public:
+  // Retrieve an AutofillWebDataService for the given context.
+  //
+  // Can return NULL in some contexts.
+  static scoped_ptr<AutofillWebDataService> ForContext(
+      content::BrowserContext* context);
+
+  virtual ~AutofillWebDataService() {}
+};
+
+#endif  // CHROME_BROWSER_API_WEBDATA_AUTOFILL_WEB_DATA_SERVICE_H_