MDL-51838 autocomplete: Scroll the suggestions list

Keep the active item "visible" when using keyboard nav on a long list of suggestions.

lib/amd/src/form-autocomplete.js

@@ -133,6 +133,15 @@ define(['jquery', 'core/log', 'core/str', 'core/templates', 'core/notification']
         element.attr('aria-selected', true).attr('id', itemId);
         // Tell the input field it has a new active descendant so the item is announced.
         inputElement.attr('aria-activedescendant', itemId);
+
+        // Scroll it into view.
+        var scrollPos = element.offset().top
+                       - suggestionsElement.offset().top
+                       + suggestionsElement.scrollTop()
+                       - (suggestionsElement.height() / 2);
+        suggestionsElement.animate({
+            scrollTop: scrollPos
+        }, 100);
     };
 
     /**