Linux: change protobuf default option to allow building

sync/protocol/session_specifics.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.
 //
 // Sync protocol datatype extension for sessions.
 
 // Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
 // any fields in this file.
 
 syntax = "proto2";
 
-option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
-
 package sync_pb;
 
 import "sync_enums.proto";
 
 message SessionSpecifics {
   // Unique id for the client.
   optional string session_tag = 1;
   optional SessionHeader header = 2;
   optional SessionTab tab = 3;
 
@@ skipping 87 matching lines @@
   // User is navigating to the home page.
   optional bool navigation_home_page = 12;
   // The beginning of a navigation chain.
   optional bool navigation_chain_start = 13;
   // The last transition in a redirect chain.
   optional bool navigation_chain_end = 14;
   // The id for this navigation, which is globally unique with high
   // probability.
   optional int64 global_id = 15;
 }