Add strict mode directive to a few more files.

test/asset/worker.js

@@ -1,3 +1,5 @@
+'use strict';
+
 self.console || (self.console = { 'log': function() {} });
 
 addEventListener('message', function(e) {

test/test-fp.js

@@ -1,4 +1,5 @@
 ;(function() {
+  'use strict';
 
   /** Used as a safe reference for `undefined` in pre-ES5 environments. */
   var undefined;