Linux: change protobuf default option to allow building

sync/protocol/get_updates_caller_info.proto

 // 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.
 
 syntax = "proto2";
 
-option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
-
 package sync_pb;
 
 message GetUpdatesCallerInfo {
   enum GetUpdatesSource {
     UNKNOWN = 0;  // The source was not set by the caller.
     FIRST_UPDATE = 1;  // First request after browser restart.  Not to
                        // be confused with "NEW_CLIENT".
     LOCAL = 2;  // The source of the update was a local change.
     NOTIFICATION = 3;  // The source of the update was a p2p notification.
     PERIODIC = 4;  // The source of the update was periodic polling.
@@ skipping 19 matching lines @@
                               // typically used when datatype's have custom
                               // sync UI, e.g. sessions.
   }
 
   required GetUpdatesSource source = 1;
 
   // True only if notifications were enabled for this GetUpdateMessage.
   optional bool notifications_enabled = 2;
 };