Mark idlharness test as timeout=long

This is symptomatic of crbug.com/1047818, but to stop the pain for
sheriffs lets mark it timeout=long for now.

TBR=lpz@chromium.org

Bug: 1085497
Change-Id: Icc9aade41e95f75c2ceda3378b3cbd6b9dfb0deb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2213407Reviewed-by: Stephen McGruer <smcgruer@chromium.org>
Reviewed-by: Luke Z <lpz@chromium.org>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771570}

third_party/blink/web_tests/external/wpt/element-timing/idlharness.window.js

 // META: script=/resources/WebIDLParser.js
 // META: script=/resources/idlharness.js
+// META: timeout=long
 
 // https://wicg.github.io/element-timing/