Also return the resulting array in GetSortedArrayKeys

BUG=

Review URL: https://codereview.chromium.org/1794233006

Cr-Commit-Position: refs/heads/master@{#34775}

src/js/array.js

@@ -88,6 +88,7 @@ function GetSortedArrayKeys(array, indices) {
         keys.push(i);
       }
     }
+    return keys;
   }
   return InnerArraySort(indices, indices.length, KeySortCompare);
 }