There are a number of steps you need to follow to actually get a builder set up.

See https://chromium.googlesource.com/chromium/tools/build.git/+/master/scripts/slave/recipe_modules/chromium_tests/chromium_recipe.md#Create-a-New-Builder 

and let me know (or, preferably, ask on infra-dev@) if you have questions.

Any chance this could also build use_platform_icu_alternatives=true which also fails (or at the least icu_use_data_file=false). All of these are failing.

I would prefer to not, since we don't set those for our internal audio builds.

I did try it though, but I cannot even do a gn gen with use_platform_icu_laternative=true because I get assert failures:
ERROR at //url/BUILD.gn:87:7: Assertion failed.
      assert(false,
      ^-----
ICU alternative is not implemented for platform: linux

icu_use_data_file=false did at least generate, but I don't think this is the right build to put it in

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/83d2305af8b3143f5c85d9d72c0c392ec88a15ba

commit 83d2305af8b3143f5c85d9d72c0c392ec88a15ba
Author: mbjorge <mbjorge@chromium.org>
Date: Sat Mar 11 00:08:29 2017

Add a cast audio bot.

This exercises the is_cast_audio_only=true and enable_webrtc=false
codepaths which periodically break because they are not built.

Corresponding CL at https://chromium-review.googlesource.com/c/452802/

BUG= 667546 
TEST=`gn gen out_audio/ --args='is_chromecast=true
is_cast_audio_only=true enable_webrtc=false' && ninja -C out_audio/
cast_shell`

Review-Url: https://codereview.chromium.org/2538883003
Cr-Commit-Position: refs/heads/master@{#456222}

[modify] https://crrev.com/83d2305af8b3143f5c85d9d72c0c392ec88a15ba/testing/buildbot/chromium.linux.json
[modify] https://crrev.com/83d2305af8b3143f5c85d9d72c0c392ec88a15ba/tools/mb/mb_config.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build/+/f30cd17e8aaf3def5994b8384da96ef56e80b3dd

commit f30cd17e8aaf3def5994b8384da96ef56e80b3dd
Author: Mike Bjorge <mbjorge@chromium.org>
Date: Sun Mar 19 21:15:29 2017

Add a cast audio bot.

The cast audio bot exercises the is_cast_audio_only=true and
enable_webrtc=false codepaths.

BUG= 667546 

Change-Id: Ia8d48ed510c1991cba87d8ea2adc46aa8a2fb7d6
Reviewed-on: https://chromium-review.googlesource.com/452802
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>

[add] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/scripts/slave/recipes/chromium.expected/full_chromium_linux_Cast_Audio_Linux.json
[modify] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/masters/master.chromium.linux/master_linux_cfg.py
[modify] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/scripts/slave/recipe_modules/chromium_tests/trybots.py
[modify] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/masters/master.chromium.linux/slaves.cfg
[add] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/scripts/slave/recipes/chromium_trybot.expected/full_tryserver_chromium_linux_cast_shell_audio_linux.json
[modify] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/masters/master.tryserver.chromium.linux/master.cfg
[modify] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/scripts/slave/recipe_modules/chromium_tests/chromium_linux.py
[modify] https://crrev.com/f30cd17e8aaf3def5994b8384da96ef56e80b3dd/masters/master.tryserver.chromium.linux/slaves.cfg

Seems like I have missed a step somewhere?
 
https://build.chromium.org/p/chromium.linux/waterfall shows the Cast Audio Linux bot as offline with 1572 builds pending.

Filed https://bugs.chromium.org/p/chromium/issues/detail?id=706165 to get a slave restart, as that may have been my missing step?

It's building now and mostly green, looks like just a config issue for a couple of the unittest suites need to get fixed

https://build.chromium.org/p/chromium.linux/builders/Cast%20Audio%20Linux has been failing from its onboard. Mind fixing?

Yes sorry, CL is going through CQ now: https://codereview.chromium.org/2777413007

Though that CL only fixes one of the issues. Filed crbug/706555 for the other issue. Not sure yet how to fix that one

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e9890b763eacc6b1034f7abc332b14eedf3c2961

commit e9890b763eacc6b1034f7abc332b14eedf3c2961
Author: mbjorge <mbjorge@chromium.org>
Date: Thu Mar 30 17:00:01 2017

[Chromecast] Fix Cast Audio Linux bot; use ozone-platform=headless.

The cast audio builds use headless instead of cast ozone platform
(see https://cs.chromium.org/chromium/src/ui/ozone/ozone.gni)

BUG= 667546 

Review-Url: https://codereview.chromium.org/2777413007
Cr-Commit-Position: refs/heads/master@{#460800}

[modify] https://crrev.com/e9890b763eacc6b1034f7abc332b14eedf3c2961/testing/buildbot/chromium.linux.json

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/829705bfdb5c38eb06f1ab014b9f7b0f317f72b9

commit 829705bfdb5c38eb06f1ab014b9f7b0f317f72b9
Author: mbjorge <mbjorge@chromium.org>
Date: Fri Mar 31 03:54:41 2017

Don't use swarming for cast_shell_browsertests on Cast Audio Linux.

Cast Audio Linux bot is failing to load files when run with swarming.
Cast Linux bot runs cast_shell_browsertests successfully not on
swarming, so try matching that for Cast Audio Linux.

BUG= 707093 ,  667546 

Review-Url: https://codereview.chromium.org/2793473002
Cr-Commit-Position: refs/heads/master@{#461019}

[modify] https://crrev.com/829705bfdb5c38eb06f1ab014b9f7b0f317f72b9/testing/buildbot/chromium.linux.json

Builder is green now! Woooo