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

chrome/browser/sync/protocol/proto_enum_conversions.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_SYNC_PROTOCOL_PROTO_ENUM_CONVERSIONS_H_
 #define CHROME_BROWSER_SYNC_PROTOCOL_PROTO_ENUM_CONVERSIONS_H_
 #pragma once
 
 // Keep this file in sync with the .proto files in this directory.
 
 #include "chrome/browser/sync/protocol/session_specifics.pb.h"
+#include "chrome/browser/sync/protocol/sync.pb.h"
 
 // Utility functions to get the string equivalent for some sync proto
 // enums.
 
 namespace browser_sync {
 
 // The returned strings (which don't have to be freed) are in ASCII.
 // The result of passing in an invalid enum value is undefined.
 
 const char* GetBrowserTypeString(
     sync_pb::SessionWindow::BrowserType browser_type);
 
 const char* GetPageTransitionString(
     sync_pb::TabNavigation::PageTransition page_transition);
 
 const char* GetPageTransitionQualifierString(
     sync_pb::TabNavigation::PageTransitionQualifier
         page_transition_qualifier);
 
 const char* GetUpdatesSourceString(
     sync_pb::GetUpdatesCallerInfo::GetUpdatesSource updates_source);
 
 const char* GetDeviceTypeString(
     sync_pb::SessionHeader::DeviceType device_type);
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_PROTOCOL_PROTO_ENUM_CONVERSIONS_H_