[USS] Implement ApplySyncChanges and OnURLVisited/Modified/Deleted.

components/history/core/browser/history_backend.cc

 // 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 "components/history/core/browser/history_backend.h"
 
 #include <algorithm>
 #include <functional>
 #include <list>
 #include <map>
@@ skipping 1024 matching lines @@
   db_->GetVisitsSource(visits, sources);
   return true;
 }
 
 bool HistoryBackend::GetURL(const GURL& url, URLRow* url_row) {
   if (db_)
     return db_->GetRowForURL(url, url_row) != 0;
   return false;
 }
 
+bool HistoryBackend::GetURLByID(URLID url_id, URLRow* url_row) {
+  if (db_)
+    return db_->GetURLRow(url_id, url_row);
+  return false;
+}
+
 void HistoryBackend::QueryURL(const GURL& url,
                               bool want_visits,
                               QueryURLResult* result) {
   DCHECK(result);
   result->success = db_ && db_->GetRowForURL(url, &result->row);
   // Optionally query the visits.
   if (result->success && want_visits)
     db_->GetVisitsForURL(result->row.id(), &result->visits);
 }
 
@@ skipping 1598 matching lines @@
   // transaction is currently open.
   db_->CommitTransaction();
   db_->Vacuum();
   db_->BeginTransaction();
   db_->GetStartDate(&first_recorded_time_);
 
   return true;
 }
 
 }  // namespace history