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

chrome/browser/sync/internal_api/change_record_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 "chrome/browser/sync/internal_api/change_record.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "base/string_number_conversions.h"
 #include "base/test/values_test_util.h"
 #include "base/values.h"
@@ skipping 57 matching lines @@
 }
 
 class MockExtraChangeRecordData
     : public ExtraPasswordChangeRecordData {
  public:
   MOCK_CONST_METHOD0(ToValue, DictionaryValue*());
 };
 
 TEST_F(ChangeRecordTest, ChangeRecordToValue) {
   sync_pb::EntitySpecifics old_specifics;
-  old_specifics.MutableExtension(sync_pb::extension)->set_id("old");
+  old_specifics.mutable_extension()->set_id("old");
   sync_pb::EntitySpecifics new_specifics;
-  old_specifics.MutableExtension(sync_pb::extension)->set_id("new");
+  old_specifics.mutable_extension()->set_id("new");
 
   const int64 kTestId = 5;
 
   // Add
   {
     ChangeRecord record;
     record.action = ChangeRecord::ACTION_ADD;
     record.id = kTestId;
     record.specifics = old_specifics;
     record.extra.reset(new StrictMock<MockExtraChangeRecordData>());
@@ skipping 37 matching lines @@
         Invoke(&extra_value, &DictionaryValue::DeepCopy));
 
     record.extra.reset(extra.release());
     scoped_ptr<DictionaryValue> value(record.ToValue());
     CheckChangeRecordValue(record, *value);
   }
 }
 
 }  // namespace
 }  // namespace sync_api