Fix the issue of skip-waiting-installed.https.html

According to the current spec, skipWaiting() promise should be resolved
earlier even in the case that the service worker state is "installed",
and then continues the activate in parallel. The test case violate that.

The background is in w3c/ServiceWorker#1015.

BUG=725616

Change-Id: Ic09b4d404ea41138c8bda8d3ced07094a7ebc6ab
Reviewed-on: https://chromium-review.googlesource.com/571612
Cr-Commit-Position: refs/heads/master@{#487024}
WPT-Export-Revision: 2256ed61b315000c27f6c8b0dd94a3f025c4adc1

Author: xzhan96

service-workers/service-worker/skip-waiting-installed.https.html

@@ -20,15 +20,15 @@
           assert_equals(
             message, 'PASS',
             'skipWaiting promise should be resolved with undefined');
-
-          assert_equals(registration.active.scriptURL, normalizeURL(url2),
-                        'skipWaiting should make worker become active');
         });
     var saw_controllerchanged = new Promise(function(resolve) {
         oncontrollerchanged = function() {
             assert_equals(
                 frame_sw.controller.scriptURL, normalizeURL(url2),
                 'Controller scriptURL should change to the second one');
+
+            assert_equals(registration.active.scriptURL, normalizeURL(url2),
+                          'skipWaiting should make worker become active');
             resolve();
         };
       });