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

components/autofill/content/renderer/autofill_agent.h

Index: components/autofill/content/renderer/autofill_agent.h
diff --git a/components/autofill/content/renderer/autofill_agent.h b/components/autofill/content/renderer/autofill_agent.h
index c71f31d4bbcd22ee47cbe119e593ecbbbb7d06ac..16c6704b883e9ccdc29ceeb7f950a0792fa57858 100644
--- a/components/autofill/content/renderer/autofill_agent.h
+++ b/components/autofill/content/renderer/autofill_agent.h
@@ -154,12 +154,13 @@ class AutofillAgent : public content::RenderFrameObserver,
   void OnClearForm();
   void OnClearPreviewedForm();
   void OnFillFieldWithValue(const base::string16& value);
-  void OnPreviewFieldWithValue(const base::string16& value);
+  void OnPreviewFieldWithValue(const base::string16& value, int match_start);
   void OnAcceptDataListSuggestion(const base::string16& value);
   void OnFillPasswordSuggestion(const base::string16& username,
                                 const base::string16& password);
   void OnPreviewPasswordSuggestion(const base::string16& username,
-                                   const base::string16& password);
+                                   const base::string16& password,
+                                   int start);
 
   // Called when interactive autocomplete finishes. |message| is printed to
   // the console if non-empty.
@@ -205,7 +206,8 @@ class AutofillAgent : public content::RenderFrameObserver,
   // visible on screen to the user, but not visible to the page via the DOM or
   // JavaScript.
   void PreviewFieldWithValue(const base::string16& value,
-                             blink::WebInputElement* node);
+                             blink::WebInputElement* node,
+                             int match_start);
 
   // Notifies browser of new fillable forms in |render_frame|.
   void ProcessForms();