Add support for json-results-file option for Junit tests.

Add support for json-results-file option for Junit tests.

The recipes need the ability to parse the test results. Adding
support for the json-results-file option so we can tell what junit
tests failed in the infra recipes.

BUG=

Committed: https://crrev.com/572401b2b3015733b3034d7482bf3fde1221bf0a
Cr-Commit-Position: refs/heads/master@{#324343}

[mikecase (-- gone --), 2015-04-08 20:56:49]

mikecase@chromium.org changed reviewers:
+ jbudorick@chromium.org

[mikecase (-- gone --), 2015-04-08 20:56:49]

Pretty much every other type of test supports this option, and I'm pretty sure
I'll need it to add the Robolectric junit tests to the main waterfall recipes.

[jbudorick, 2015-04-08 20:58:02]

lgtm

[mikecase (-- gone --), 2015-04-08 20:59:47]

The CQ bit was checked by mikecase@chromium.org

[commit-bot: I haz the power, 2015-04-08 21:00:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1062403004/1

[commit-bot: I haz the power, 2015-04-09 02:29:10]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-09 02:30:50]

Patchset 1 (id:??) landed as
https://crrev.com/572401b2b3015733b3034d7482bf3fde1221bf0a
Cr-Commit-Position: refs/heads/master@{#324343}