Create an AutofillBackend interface

components/webdata/common/web_database_service.cc

Index: components/webdata/common/web_database_service.cc
diff --git a/components/webdata/common/web_database_service.cc b/components/webdata/common/web_database_service.cc
index baef346b113b8596a88d9a7d95756684ef0023e1..fbcc92a2f7948f36d63d3b57ddf3d003e9a15e8f 100644
--- a/components/webdata/common/web_database_service.cc
+++ b/components/webdata/common/web_database_service.cc
@@ -84,6 +84,12 @@ void WebDatabaseService::ShutdownDatabase() {
            wds_backend_, false));
 }
 
+void WebDatabaseService::GetDatabaseOnDB(const DBCallback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
+      Bind(&WebDataServiceBackend::GetDatabaseAsync, wds_backend_, callback));
+}
+
 WebDatabase* WebDatabaseService::GetDatabaseOnDB() const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::DB));
   if (!wds_backend_)