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

chrome/browser/sync/profile_sync_service_session_unittest.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 <map>
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
@@ skipping 664 matching lines @@
 
 // Test the DataTypeController on delete.
 TEST_F(ProfileSyncServiceSessionTest, UpdatedSyncNodeActionDelete) {
   CreateRootHelper create_root(this);
   ASSERT_TRUE(StartSyncService(create_root.callback(), false));
   ASSERT_TRUE(create_root.success());
 
   int64 node_id = model_associator_->GetSyncIdFromSessionTag(
       model_associator_->GetCurrentMachineTag());
   sync_pb::EntitySpecifics deleted_specifics;
-  deleted_specifics.MutableExtension(sync_pb::session)->set_session_tag("tag");
+  deleted_specifics.mutable_session()->set_session_tag("tag");
   ASSERT_FALSE(notified_of_update_);
   {
     sync_api::WriteTransaction trans(FROM_HERE, sync_service_->GetUserShare());
     change_processor_->ApplyChangesFromSyncModel(
         &trans,
         ProfileSyncServiceTestHelper::MakeSingletonDeletionChangeRecordList(
             node_id, deleted_specifics));
   }
   ASSERT_TRUE(notified_of_update_);
 }
@@ skipping 303 matching lines @@
           GetEntryAtIndex(1)->GetVirtualURL());
   iter++;
   ASSERT_EQ(2, iter->second.tab()->GetEntryCount());
   ASSERT_EQ(GURL("http://bar1"), iter->second.tab()->
       GetEntryAtIndex(0)->GetVirtualURL());
   ASSERT_EQ(GURL("http://bar2"), iter->second.tab()->
       GetEntryAtIndex(1)->GetVirtualURL());
 }
 
 }  // namespace browser_sync