Include the referrer policy in sync'd tab navigations

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";
@@ skipping 116 matching lines @@
   enum BlockedState {
     STATE_ALLOWED = 1;
     STATE_BLOCKED = 2;
   }
   // Whether access to the URL was allowed or blocked.
   optional BlockedState blocked_state = 18 [default=STATE_ALLOWED];
   // A list of category identifiers for the URL.
   repeated string content_pack_categories = 19;
   // The status code from the last navigation.
   optional int32 http_status_code = 20;
+  // Referrer policy.
+  optional int32 referrer_policy = 21;
 }