Gardening: Mark textfieldselection/selection as slow/failing

Gardening: Mark textfieldselection/selection as slow/failing

This appears to have been failing on debug bots since it was
committed.

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=imported%2Fweb-platform-tests%2Fhtml%2Fsemantics%2Fforms%2Ftextfieldselection%2Fselection.html&testType=layout-tests

NOTRY=true
TBR=tkent@chromium.org,dstockwell@chromium.org
BUG=490511
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196699

[enne (OOO), 2015-06-08 21:41:09]

The CQ bit was checked by enne@chromium.org

[commit-bot: I haz the power, 2015-06-08 21:41:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1167323002/1

[commit-bot: I haz the power, 2015-06-08 21:45:39]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196699

[tkent, 2015-06-08 23:10:14]

lgtm.  thank you!