Don't demote top match for certain match types.

chrome/browser/autocomplete/autocomplete_match.h

Index: chrome/browser/autocomplete/autocomplete_match.h
diff --git a/chrome/browser/autocomplete/autocomplete_match.h b/chrome/browser/autocomplete/autocomplete_match.h
index 38108dda8e0226647be53b4a0a01f6cfbdb43f8a..1cb8cbbd1f466704288347ac280aa548b109667a 100644
--- a/chrome/browser/autocomplete/autocomplete_match.h
+++ b/chrome/browser/autocomplete/autocomplete_match.h
@@ -271,6 +271,10 @@ struct AutocompleteMatch {
   // should set this flag.
   bool allowed_to_be_default_match;
 
+  // If the match should be allowed to be demoted by OmniboxBundleV1 ranking
+  // experiments.
+  bool demoteable;
+
   // The URL to actually load when the autocomplete item is selected. This URL
   // should be canonical so we can compare URLs with strcmp to avoid dupes.
   // It may be empty if there is no possible navigation.