Revert of Mark ui_base_unittests target to be used on Swarming.

Revert of Mark ui_base_unittests target to be used on Swarming. (patchset #2 id:20001 of https://codereview.chromium.org/1063603002/)

Reason for revert:
Turns "isolate tests" red on some bots, reverting while maruel investigates: http://build.chromium.org/p/chromium.fyi/builders/CrWinClang%28dbg%29/builds/765/steps/isolate%20tests/logs/stdio

Original issue's description:
> Mark ui_base_unittests target to be used on Swarming.
>
> Patch generated with the following command line:
>
> $ ./testing/buildbot/manage.py --convert ui_base_unittests
>
> BUG=98637
> TEST=trybots?
> R=maruel@chromium.org
>
> Committed: https://crrev.com/79e2c2139c83ccc50de4a73288eac94ab13b94f0
> Cr-Commit-Position: refs/heads/master@{#333991}

TBR=maruel@chromium.org,tfarina@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=98637
Committed: https://crrev.com/6b2a998c601aec800ad1f0f30b2369fd49a9580b
Cr-Commit-Position: refs/heads/master@{#334051}

[Nico, 2015-06-11 22:07:38]

Created Revert of Mark ui_base_unittests target to be used on Swarming.

[M-A Ruel, 2015-06-11 22:08:25]

On 2015/06/11 22:07:38, Nico wrote:
> Created Revert of Mark ui_base_unittests target to be used on Swarming.

Well, my point was to not revert the whole CL.

[commit-bot: I haz the power, 2015-06-11 22:08:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1179083002/1

[commit-bot: I haz the power, 2015-06-11 22:11:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-11 22:13:18]

Patchset 1 (id:??) landed as
https://crrev.com/6b2a998c601aec800ad1f0f30b2369fd49a9580b
Cr-Commit-Position: refs/heads/master@{#334051}

[Nico, 2015-06-11 22:14:28]

Oh sorry, I thought that's what you meant with unblocking :-/

I looked around a bit, I think the problem might be that build/all.gyp doesn't
list ui_base_unittests_run in chromium_swarm_tests. The clang bots build "all"
targets, which means the targets referenced directly by build/all.gyp get built.
So that's probably why it doesn't isolate that specific test.