Fix GN auto-roller to handle results from buildbucket-initiated jobs.

Fix GN auto-roller to handle results from buildbucket-initiated jobs.

It looks like we can get returned a try job state value of -1 now
when the try jobs are run through buildbucket instead of rietveld,
so this change updates the status mapping accordingly.

R=brettw@chromium.org
BUG=

Committed: https://crrev.com/84ffc7ef400da2351d559211bcdeeba20634df54
Cr-Commit-Position: refs/heads/master@{#348266}

[brettw, 2015-09-10 22:01:37]

lgtm

[Dirk Pranke, 2015-09-10 22:06:48]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-09-10 22:07:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1336713002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1336713002/1

[commit-bot: I haz the power, 2015-09-10 22:44:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-10 22:45:28]

Patchset 1 (id:??) landed as
https://crrev.com/84ffc7ef400da2351d559211bcdeeba20634df54
Cr-Commit-Position: refs/heads/master@{#348266}

[commit-bot: I haz the power, 2015-09-23 12:15:35]

Patchset 1 (id:??) landed as
https://crrev.com/84ffc7ef400da2351d559211bcdeeba20634df54
Cr-Commit-Position: refs/heads/master@{#348266}