Fix flakiness of imported/web-platform-tests/html/syntax/parsing/html5lib_testsNN.html.

LayoutTests/http/tests/resources/testharnessreport.js

Index: LayoutTests/http/tests/resources/testharnessreport.js
diff --git a/LayoutTests/http/tests/resources/testharnessreport.js b/LayoutTests/http/tests/resources/testharnessreport.js
index 57793a3d1b5e8595297f7ec8b3a78f73a44ca33e..86873d816e61c752327b272df1fe76d378a4aae1 100644
--- a/LayoutTests/http/tests/resources/testharnessreport.js
+++ b/LayoutTests/http/tests/resources/testharnessreport.js
@@ -126,6 +126,6 @@ add_completion_callback(function (tests, harness_status) {
     if (document.readyState === 'loading') {
         window.addEventListener('load', done);
     } else {
-        done();
+        setTimeout(done, 0);
     }
 });