sync: remove use of protobuf extensions in protocol to reduce static init overhead.

chrome/browser/sync/glue/session_change_processor.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 "chrome/browser/sync/glue/session_change_processor.h"
 
 #include <string>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 246 matching lines @@
   for (sync_api::ChangeRecordList::const_iterator it =
            changes.Get().begin(); it != changes.Get().end(); ++it) {
     const sync_api::ChangeRecord& change = *it;
     sync_api::ChangeRecord::Action action(change.action);
     if (sync_api::ChangeRecord::ACTION_DELETE == action) {
       // Deletions are all or nothing (since we only ever delete entire
       // sessions). Therefore we don't care if it's a tab node or meta node,
       // and just ensure we've disassociated.
       DCHECK_EQ(syncable::GetModelTypeFromSpecifics(it->specifics),
                 syncable::SESSIONS);
-      const sync_pb::SessionSpecifics& specifics =
-          it->specifics.GetExtension(sync_pb::session);
+      const sync_pb::SessionSpecifics& specifics = it->specifics.session();
       session_model_associator_->DisassociateForeignSession(
           specifics.session_tag());
       continue;
     }
 
     // Handle an update or add.
     sync_api::ReadNode sync_node(trans);
     if (!sync_node.InitByIdLookup(change.id)) {
       error_handler()->OnSingleDatatypeUnrecoverableError(FROM_HERE,
           "Session node lookup failed.");
@@ skipping 64 matching lines @@
       content::NotificationService::AllBrowserContextsAndSources());
 }
 
 void SessionChangeProcessor::StopObserving() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(profile_);
   notification_registrar_.RemoveAll();
 }
 
 }  // namespace browser_sync