Upstream service worker tests to WPT

third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/resources/install-event-type-worker.js

 importScripts('worker-testharness.js');
 
 self.oninstall = function(event) {
-    assert_true(event instanceof ExtendableEvent);
-    assert_equals(event.type, 'install');
-    assert_false(event.cancelable);
-    assert_false(event.bubbles);
+    assert_true(event instanceof ExtendableEvent, 'instance of ExtendableEvent');
+    assert_true(event instanceof InstallEvent, 'instance of InstallEvent');
+    assert_equals(event.type, 'install', '`type` property value');
+    assert_false(event.cancelable, '`cancelable` property value');
+    assert_false(event.bubbles, '`bubbles` property value');
 };