Bug 1559346 [wpt PR 17344] - Convert Long Tasks API idlharness test to use `idl_test`, a=testonly

Automatic update from web-platform-tests
Convert Long Tasks API idlharness test to use `idl_test` (#17344)

Because the setup function is allowed to fail, this makes the setup a
bit simpler.

This is to make it easier to add 'hr-time' as a dependency for
https://github.com/web-platform-tests/wpt/pull/17305.
--

wpt-commits: e5167a1ffdd432f1fadd721d63fd1cf42bd67e96
wpt-pr: 17344

testing/web-platform/tests/longtask-timing/idlharness.window.js

@@ -1,51 +1,34 @@
 // META: script=/resources/WebIDLParser.js
 // META: script=/resources/idlharness.js
 
-// https://w3c.github.io/longtask-timing/
+// https://w3c.github.io/longtasks/
 
 'use strict';
 
-promise_test(async t => {
-  const srcs = ['longtasks', 'performance-timeline'];
-  const [idl, perf] = await Promise.all(
-    srcs.map(i => fetch(`/interfaces/${i}.idl`).then(r => r.text())));
-
-  const idl_array = new IdlArray();
-  idl_array.add_idls(idl);
-  idl_array.add_dependency_idls(perf);
-
-  const testIdls = new Promise(resolve => {
-    try {
-      const observer = new PerformanceObserver(entryList => {
-        const entries = Array.from(entryList.getEntries());
-        const attribution = entries.reduce(
-            (sum, e) => sum.concat(e.attribution || []), []);
-        idl_array.add_objects({
-          PerformanceLongTaskTiming: entries,
-          TaskAttributionTiming: attribution,
-        });
-        idl_array.test();
-        resolve();
-      });
-      observer.observe({entryTypes: ['longtask']});
-    } catch (e) {
-      // Will be surfaces in idlharness.js's test_object below.
+idl_test(
+  ['longtasks'],
+  ['performance-timeline'],
+  (idl_array, t) => new Promise((resolve, reject) => {
+    const longTask = () => {
+      const begin = self.performance.now();
+      while (self.performance.now() < begin + 100);
     }
-  });
+    t.step_timeout(longTask, 0);
 
-  const longTask = () => {
-    var begin = self.performance.now();
-    while (self.performance.now() < begin + 100);
-  }
-  t.step_timeout(longTask, 0);
+    const observer = new PerformanceObserver(entryList => {
+      const entries = Array.from(entryList.getEntries());
+      const attribution = entries.reduce(
+          (sum, e) => sum.concat(e.attribution || []), []);
+      idl_array.add_objects({
+        PerformanceLongTaskTiming: entries,
+        TaskAttributionTiming: attribution,
+      });
+      resolve();
+    });
+    observer.observe({entryTypes: ['longtask']});
 
-  const timeout = new Promise(
-      (_, reject) => t.step_timeout(reject, 1000));
-  return Promise.race([testIdls, timeout])
-    .then(
-        t.step_func_done(),
-        () => {
-          idl_array.test(); // Rejected, but test what we can.
-          return Promise.reject('LongTask was not observed');
-        });
-}, 'longtasks interfaces');
+    t.step_timeout(() => {
+      reject('longtask entry was not observed');
+    }, 1000);
+  })
+);