Add search_terms_replacement_key field to TemplateURL.

sync/protocol/search_engine_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 custom search engines.
 
 // Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
 // any fields in this file.
 
 syntax = "proto2";
@@ skipping 44 matching lines @@
   optional string instant_url = 15;
   // ID 16 reserved - previously used by |id|, now deprecated.
   // The last time this entry was modified by a user. A UTC timestamp with units
   // in microseconds.
   optional int64 last_modified = 17;
   // The primary identifier of this search engine entry for Sync.
   optional string sync_guid = 18;
   // A list of URL patterns that can be used, in addition to |url| and
   // |instant_url|, to extract search terms from a URL.
   repeated string alternate_urls = 19;
+  // Parameter that, if present in a search URL, indicates that Chrome should
+  // perform search terms replacement in the omnibox.
+  optional string search_terms_replacement_key = 20;
 }