FLAKY TEST on dartium windows: html/html_tests

[ricowind]

html/html_tests seems to have flaked on the windows incremental dartium bot:
http://build.chromium.org/p/client.dart/builders/dartium-win-inc/builds/600/steps/annotated_steps/logs/stdio

A forced build on the buildbot made it green, and subsequent builds are also green.

I did not mark this in the status file

[DartBot]

This comment was originally written by antonm@google.com

---

Set owner to antonm@google.com.

[DartBot]

This comment was originally written by antonm@google.com

---

Added Duplicate label.
Marked as being merged into #1946.