Add search_terms_replacement_key field to TemplateURL.

sync/protocol/search_engine_specifics.proto

Index: sync/protocol/search_engine_specifics.proto
diff --git a/sync/protocol/search_engine_specifics.proto b/sync/protocol/search_engine_specifics.proto
index 200255ba5c83bc4dd8e41b35bc322cf56589b822..cc5db7272cd34dfdd465f91b716e3e4e0db731b4 100644
--- a/sync/protocol/search_engine_specifics.proto
+++ b/sync/protocol/search_engine_specifics.proto
@@ -62,5 +62,8 @@ message SearchEngineSpecifics {
   // 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;
 }