Reland "Build delegation for perf tryjobs"

Reland issue: https://codereview.chromium.org/2103133005/

In original issue, build_state.is_completed is checking for stdout['status'] instead of
stdout['build']['status']

BUG=

Committed: https://chromium.googlesource.com/chromium/tools/build/+/c62890265b947bf33fe45001298f3522ae205a01

[Ziqi Xiong, 2016-06-30 20:30:53]

zxiong@google.com changed reviewers:
+ robertocn@chromium.org

[Ziqi Xiong, 2016-06-30 20:30:54]

new cl on build delegation that fixes the key error

[RobertoCN, 2016-06-30 21:26:59]

On 2016/06/30 20:30:54, Ziqi Xiong wrote:
> new cl on build delegation that fixes the key error

Modify issue subject to say `Reland of 'Build delegation...'` and also link to
the last cl that was reverted with note on what was wrong.

[Ziqi Xiong, 2016-06-30 21:32:55]

Description was changed from

==========
Build delegation for perf tryjobs (fix key error in buildstate.py)
This CL attempts to implement build delegation for perf tryjobs.
Currently, perf try jobs build on the same builder that runs the test.
This is bad because often we want much slower performance characteristics on
our perfbots than on our builders, and this makes the builds very slow or even
impossible.
BUG=
==========

to

==========
Reland issue: https://codereview.chromium.org/2103133005/

In original issue, build_state.is_completed is checking for stdout['status']
instead of
stdout['build']['status']

BUG=
==========

[RobertoCN, 2016-06-30 22:24:04]

The CQ bit was checked by robertocn@chromium.org

[RobertoCN, 2016-06-30 22:24:04]

lgtm

[commit-bot: I haz the power, 2016-06-30 22:24:14]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-06-30 22:28:54]

Description was changed from

==========
Reland issue: https://codereview.chromium.org/2103133005/

In original issue, build_state.is_completed is checking for stdout['status']
instead of
stdout['build']['status']

BUG=
==========

to

==========
Reland issue: https://codereview.chromium.org/2103133005/

In original issue, build_state.is_completed is checking for stdout['status']
instead of
stdout['build']['status']

BUG=

Committed:
https://chromium.googlesource.com/chromium/tools/build/+/c62890265b947bf33fe4...
==========

[commit-bot: I haz the power, 2016-06-30 22:28:55]

Committed patchset #2 (id:10001) as
https://chromium.googlesource.com/chromium/tools/build/+/c62890265b947bf33fe4...

[RobertoCN, 2016-06-30 23:19:06]

A revert of this CL (patchset #2 id:10001) has been created in
https://codereview.chromium.org/2117643002/ by robertocn@chromium.org.

The reason for reverting is: There is a problem with the build request's
formatting.

The field `buildername` should be called `builder_name`

Please fix this and re-land.