Introduce a couple of abstract bases for WebDataService.

chrome/browser/webdata/web_data_service.cc

Index: chrome/browser/webdata/web_data_service.cc
diff --git a/chrome/browser/webdata/web_data_service.cc b/chrome/browser/webdata/web_data_service.cc
index 84514fe7a6b367dcb7f81f9fdbc23cbf38ebfbb0..c893cd426f016bf72efe2f692ddbb193b22ae125 100644
--- a/chrome/browser/webdata/web_data_service.cc
+++ b/chrome/browser/webdata/web_data_service.cc
@@ -67,6 +67,11 @@ void NotifyOfMultipleAutofillChangesTask(
 
 }  // namespace
 
+// static
+AutofillWebData* AutofillWebData::ForService(WebDataServiceBase* service) {
+  return static_cast<WebDataService*>(service);
+}
+
 WDAppImagesResult::WDAppImagesResult() : has_all_images(false) {}
 
 WDAppImagesResult::~WDAppImagesResult() {}
@@ -81,8 +86,7 @@ WDKeywordsResult::WDKeywordsResult()
 WDKeywordsResult::~WDKeywordsResult() {}
 
 WebDataService::WebDataService()
-    : RefcountedProfileKeyedService(BrowserThread::UI),
-      is_running_(false),
+    : is_running_(false),
       db_(NULL),
       autocomplete_syncable_service_(NULL),
       autofill_profile_syncable_service_(NULL),