Use asserts in origin trials layout tests

third_party/WebKit/LayoutTests/http/tests/origin_trials/webexposed/resources/foreignfetch-origin-trial-interfaces-worker-disabled.js

Index: third_party/WebKit/LayoutTests/http/tests/origin_trials/webexposed/resources/foreignfetch-origin-trial-interfaces-worker-disabled.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/origin_trials/webexposed/resources/foreignfetch-origin-trial-interfaces-worker-disabled.js b/third_party/WebKit/LayoutTests/http/tests/origin_trials/webexposed/resources/foreignfetch-origin-trial-interfaces-worker-disabled.js
new file mode 100644
index 0000000000000000000000000000000000000000..fac292b88d4b1616843ee49e9e40fe41ef689733
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/http/tests/origin_trials/webexposed/resources/foreignfetch-origin-trial-interfaces-worker-disabled.js
@@ -0,0 +1,13 @@
+importScripts('../../../resources/testharness.js');
+importScripts('../../../resources/origin-trials-helper.js');
+
+test(t => {
+  OriginTrialsHelper.check_properties_missing(this,
+    {'InstallEvent':['registerForeignFetch'],
+     'global':['onforeignfetch']});
+}, 'ForeignFetch related properties on interfaces in service worker, without trial.');
+
+test(t => {
+  OriginTrialsHelper.check_interfaces_missing(this,
+    ['ForeignFetchEvent']);
+}, 'ForeignFetch related interfaces in service worker, without trial.');