Reland of Add a library for running external commands, providing timeouts and test injection.

Reland of Add a library for running external commands, providing timeouts and test injection. (patchset #1 id:1 of https://codereview.chromium.org/1295043002/ )

Reason for revert:
Fixed bug in original code - see patchset #2.

Original issue's description:
> Revert of Add a library for running external commands, providing timeouts and test injection. (patchset #2 id:40001 of https://codereview.chromium.org/1290913004/ )
> 
> Reason for revert:
> CT Chromium Perf tasks are failing with:
> 
> E0815 11:07:22.649344   13091 exec.go:193] Command exited with invalid argument: python /b/skia-repo/go/src/go.skia.org/infra/ct/py/sync_skia_in_chrome.py --destination=/b/storage/chromium_builds/linux_base --fetch_target=chromium --chrome_revision=6ae54795f6d077e31f4fb42540ead46f4141f2bb --skia_revision=fb28cd2b13d76c324570341e1155aaadc1b532b6
> 
> Original issue's description:
> > Add a library for running external commands, providing timeouts and test injection.
> > 
> > BUG=skia:4106
> > 
> > Committed: https://skia.googlesource.com/buildbot/+/b65fde6749a3e060938cd280c7e281e29516edc1
> 
> TBR=jcgregorio@google.com,benjaminwagner@google.com
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=skia:4106
> 
> Committed: https://skia.googlesource.com/buildbot/+/ac6c1292955c888d35f6c01cf97d3b6ff4029424

BUG=skia:4106
Committed: https://skia.googlesource.com/buildbot/+/a12e89205d4145b4da14b0a7d5b95b15b029ada9

[dogben, 2015-08-18 20:05:26]

Created Reland of Add a library for running external commands, providing
timeouts and test injection.

[dogben, 2015-08-18 20:08:55]

PTAL

[rmistry, 2015-08-19 12:41:16]

lgtm

[dogben, 2015-08-19 19:48:57]

The CQ bit was checked by benjaminwagner@google.com

[commit-bot: I haz the power, 2015-08-19 19:49:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1302513006/140001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1302513006/140001

[commit-bot: I haz the power, 2015-08-19 19:51:05]

Committed patchset #2 (id:140001) as
https://skia.googlesource.com/buildbot/+/a12e89205d4145b4da14b0a7d5b95b15b029...

[rmistry, 2015-08-19 20:11:33]

A revert of this CL (patchset #2 id:140001) has been created in
https://codereview.chromium.org/1299493004/ by rmistry@google.com.

The reason for reverting is: CT Perf tasks are immediately failing:
https://uberchromegw.corp.google.com/i/skia-ct-master/run_chromium_perf_on_wo...

It is likely unrelated to this CL but I am going to try reverting it and
rerunning to see what happens..

[rmistry, 2015-08-19 20:18:00]

On 2015/08/19 20:11:33, rmistry wrote:
> A revert of this CL (patchset #2 id:140001) has been created in
> https://codereview.chromium.org/1299493004/ by mailto:rmistry@google.com.
> 
> The reason for reverting is: CT Perf tasks are immediately failing:
>
https://uberchromegw.corp.google.com/i/skia-ct-master/run_chromium_perf_on_wo...
> 
> It is likely unrelated to this CL but I am going to try reverting it and
> rerunning to see what happens..

It appears to be working after the revert:
https://uberchromegw.corp.google.com/i/skia-ct-master/run_chromium_perf_on_wo...

Sorry I could not find more useful logs. I am not sure why whichever error
caused it to crash the first time does not show up.

[dogben, 2015-08-20 02:01:39]

Patchset #3 (id:160001) has been deleted