[Trusted Types] Replace setTimeout with step_timeout in WPT test.

Bug: 1033101
Change-Id: I01638e133321abcb0604bfd9f8d72bff61425f69
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2050266Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Commit-Queue: Daniel Vogelheim <vogelheim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#740590}

third_party/blink/web_tests/external/wpt/lint.whitelist

@@ -203,7 +203,6 @@ SET TIMEOUT: shadow-dom/scroll-to-the-fragment-in-shadow-tree.html
 SET TIMEOUT: shadow-dom/slotchange-event.html
 SET TIMEOUT: trusted-types/block-string-assignment-to-DOMWindowTimers-setTimeout-setInterval.tentative.html
 SET TIMEOUT: trusted-types/DOMWindowTimers-setTimeout-setInterval.tentative.html
-SET TIMEOUT: trusted-types/HTMLScriptElement-internal-slot.tentative.html
 SET TIMEOUT: user-timing/*
 SET TIMEOUT: web-animations/timing-model/animations/*
 SET TIMEOUT: webaudio/the-audio-api/the-mediaelementaudiosourcenode-interface/mediaElementAudioSourceToScriptProcessorTest.html

third_party/blink/web_tests/external/wpt/trusted-types/HTMLScriptElement-internal-slot.tentative.html

@@ -25,7 +25,7 @@
       if (script) {
         script.appendChild(frame.contentDocument.createTextNode("/*byapi*/"));
       } else {
-        setTimeout(manipulator, 100);
+        t.step_timeout(manipulator, 100);
       }
     }
     manipulator();