Chromecast: test support for builders.

Chromecast: test support for builders.

Adds GYP targets that dictate which tests should be run on the
builders, and scripts to generate lists of the targets and commands
to run (with filters or other options as needed).

R=lcwu@chromium.org,gusfernandez@chromium.org
BUG=409163
Committed: https://crrev.com/0bf377647b4b9cd68a842a7d65d6a3e90e3b8493
Cr-Commit-Position: refs/heads/master@{#304963}

[lcwu1, 2014-11-20 00:56:23]

lgtm

[gunsch, 2014-11-20 01:41:18]

The CQ bit was checked by gunsch@chromium.org

[commit-bot: I haz the power, 2014-11-20 01:42:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/719353005/20001

[commit-bot: I haz the power, 2014-11-20 03:44:36]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-11-20 03:45:24]

Patchset 2 (id:??) landed as
https://crrev.com/0bf377647b4b9cd68a842a7d65d6a3e90e3b8493
Cr-Commit-Position: refs/heads/master@{#304963}