Fix ESLint errors in benchmark/index.js

Fix the following errors:

  74:14  error  "benchmarks" is not defined       no-undef
  84:36  error  "test" is defined but never used  no-unused-vars

benchmark/index.js

@@ -1,5 +1,5 @@
 /* eslint-env browser, jquery */
-/* global Runner */
+/* global benchmarks, Runner */
 
 $("#run").click(function() {
   "use strict";
@@ -81,7 +81,7 @@ $("#run").click(function() {
       }).responseText;
     },
 
-    testStart: function(benchmark, test) {
+    testStart: function() {
       /* Nothing to do. */
     },