Convert garden-o-matic guts over to promises where appropriate

Convert garden-o-matic guts over to promises where appropriate

This gets rid of all one-shot callbacks in favor of promises. There are
a few "progress" style callbacks which don't need to be converted.

R=abarth@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=167530

[alecflett, 2014-02-20 01:12:40]

More cleanup: this converts everything to promises. There are still a few things
to clean up (some uses of Promises.all are kinda ugly) but I am working on those
in a future patch

[abarth-chromium, 2014-02-20 06:18:51]

LGTM

Thanks for doing this!

https://codereview.chromium.org/173133003/diff/1/Tools/GardeningServer/script...
File Tools/GardeningServer/scripts/base.js (left):

https://codereview.chromium.org/173133003/diff/1/Tools/GardeningServer/script...
Tools/GardeningServer/scripts/base.js:159: base.RequestTracker =
function(requestsInFlight, callback, args)
\o/

[alecflett, 2014-02-20 16:01:02]

The CQ bit was checked by alecflett@chromium.org

[commit-bot: I haz the power, 2014-02-20 16:01:14]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/alecflett@chromium.org/173133003/1

[commit-bot: I haz the power, 2014-02-20 19:04:35]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-02-20 19:04:36]

Retried try job too often on win_blink_rel for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_blink_...

[abarth-chromium, 2014-02-20 19:10:04]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-02-20 19:10:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/alecflett@chromium.org/173133003/1

[alecflett, 2014-02-20 19:46:47]

Committed patchset #2 manually as r167530 (presubmit successful).