Convert message_center_unittests to run exclusively on Swarming

Convert message_center_unittests to run exclusively on Swarming

5 configs already ran on Swarming
8 used to run locally and were converted:
- chromium.chromiumos.json: Linux ChromiumOS Ozone Tests (1)
- chromium.chromiumos.json: Linux ChromiumOS Tests (1)
- chromium.chromiumos.json: Linux ChromiumOS Tests (dbg)(1)
- chromium.memory.json: Linux Chromium OS ASan LSan Tests (1)
- chromium.webkit.json: Linux ChromiumOS Tests (1)
- chromium.webkit.json: Linux ChromiumOS Tests (dbg)(1)
- chromium.win.json: Win 7 Tests x64 (1)
- chromium.win.json: Win7 Tests (1)

Ran:
  ./manage.py --convert message_center_unittests

R=dpranke@chromium.org
BUG=98637
Committed: https://crrev.com/f3c74c70cf5d28d414711a6f0aa45240aa36390d
Cr-Commit-Position: refs/heads/master@{#336260}

[Dirk Pranke, 2015-06-25 20:13:57]

lgtm

[M-A Ruel, 2015-06-25 20:25:49]

The CQ bit was checked by maruel@chromium.org

[commit-bot: I haz the power, 2015-06-25 20:26:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1204413002/1

[commit-bot: I haz the power, 2015-06-25 21:37:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-25 21:39:05]

Patchset 1 (id:??) landed as
https://crrev.com/f3c74c70cf5d28d414711a6f0aa45240aa36390d
Cr-Commit-Position: refs/heads/master@{#336260}