Limit the number of history urls indexed for omnibox suggestions.

components/history/core/browser/url_database.h

Index: components/history/core/browser/url_database.h
diff --git a/components/history/core/browser/url_database.h b/components/history/core/browser/url_database.h
index 1b8a5d71ee6f870dc61f5cc36cf315ebd9cf85bc..19609d1ce3baf18ac73af2ab7dabff01356b180c 100644
--- a/components/history/core/browser/url_database.h
+++ b/components/history/core/browser/url_database.h
@@ -150,9 +150,9 @@ class URLDatabase {
   bool InitURLEnumeratorForEverything(URLEnumerator* enumerator);
 
   // Initializes the given enumerator to enumerator all URLs in the database
-  // that are historically significant: ones having been visited within 3 days,
-  // having their URL manually typed more than once, or having been visited
-  // more than 3 times.
+  // that are historically significant: ones having their URL manually typed
+  // more than once, having been visited within 3 days, or having been visited
+  // more than 3 times in the order of the most significant ones first.
   bool InitURLEnumeratorForSignificant(URLEnumerator* enumerator);
 
   // Autocomplete --------------------------------------------------------------