[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/core/browser/autofill_popup_delegate.h

Index: components/autofill/core/browser/autofill_popup_delegate.h
diff --git a/components/autofill/core/browser/autofill_popup_delegate.h b/components/autofill/core/browser/autofill_popup_delegate.h
index 99a66758a30bbebf60f074f5b3027c290dade242..cf1fc918d5bc42a0c6c75c5ea53615ea5412e7b3 100644
--- a/components/autofill/core/browser/autofill_popup_delegate.h
+++ b/components/autofill/core/browser/autofill_popup_delegate.h
@@ -22,7 +22,8 @@ class AutofillPopupDelegate {
   // Called when the autofill suggestion indicated by |identifier| has been
   // temporarily selected (e.g., hovered).
   virtual void DidSelectSuggestion(const base::string16& value,
-                                   int identifier) = 0;
+                                   int identifier,
+                                   size_t match_start) = 0;
 
   // Inform the delegate that a row in the popup has been chosen.
   virtual void DidAcceptSuggestion(const base::string16& value,