Import w3c tests for the service workers

third_party/WebKit/LayoutTests/imported/wpt/service-workers/service-worker/resources/skip-waiting-worker.js

 importScripts('worker-testharness.js');
 
 promise_test(function() {
-    return self.skipWaiting()
+    return skipWaiting()
       .then(function(result) {
           assert_equals(result, undefined,
                         'Promise should be resolved with undefined');
         })
       .then(function() {
           var promises = [];
           for (var i = 0; i < 8; ++i)
             promises.push(self.skipWaiting());
           return Promise.all(promises);
         })
       .then(function(results) {
           results.forEach(function(r) {
               assert_equals(r, undefined,
                             'Promises should be resolved with undefined');
             });
         });
   }, 'skipWaiting');