Upstream service wrkr "skipWaiting" tests to WPT

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/skip-waiting-worker.js

-importScripts('worker-testharness.js');
-
-promise_test(function() {
-    return self.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');