[Autofill] Add a new metric for upstream.

components/autofill/core/browser/autofill_metrics.h

Index: components/autofill/core/browser/autofill_metrics.h
diff --git a/components/autofill/core/browser/autofill_metrics.h b/components/autofill/core/browser/autofill_metrics.h
index b8e569baf697decbc73e158ec4996a1c81f7f1db..974f39d96d77b1cc0f6a9c70399bc7f3df46a2f5 100644
--- a/components/autofill/core/browser/autofill_metrics.h
+++ b/components/autofill/core/browser/autofill_metrics.h
@@ -383,6 +383,13 @@ class AutofillMetrics {
     FORM_EVENT_LOCAL_SUGGESTION_WILL_SUBMIT_ONCE,
     FORM_EVENT_SERVER_SUGGESTION_WILL_SUBMIT_ONCE,
     FORM_EVENT_MASKED_SERVER_CARD_SUGGESTION_WILL_SUBMIT_ONCE,
+    // A dropdown with suggestions was shown and a form was submitted after
+    // that.
+    FORM_EVENT_SUGGESTION_SHOWN_SUBMITTED_ONCE,
+    // A dropdown with suggestions was shown and a form is about to be
+    // submitted. If the submission is not interrupted by JavaScript, the "form
+    // submitted" event above will also be logged.
+    FORM_EVENT_SUGGESTION_SHOWN_WILL_SUBMIT_ONCE,
 
     NUM_FORM_EVENTS,
   };