Bug 1576234 [wpt PR 18643] - Update wpt metadata, a=testonly

wpt-pr: 18643 wpt-type: metadata
2019-08-29 15:22:18 +00:00 · 2019-08-29 15:22:18 +00:00 · 6151c64e55
--- a/testing/web-platform/meta/longtask-timing/long-microtask.window.js.ini
+++ b/testing/web-platform/meta/longtask-timing/long-microtask.window.js.ini
@ -0,0 +1,4 @@
+[long-microtask.window.html]
+  [A short task followed by a long microtask is observable.]
+    expected: FAIL
+