[Telemetry] Speed up unittests on mac by about 10s.

[Telemetry] Speed up unittests on mac by about 10s.

No need to have unittests repeatedly check the USB devices.

BUG=388256
TBR=baxley@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290112

[baxley, 2014-08-15 22:17:53]

LGTM. Thanks, I'll rebase this to the backend CL in-flight.

[tonyg, 2014-08-15 22:34:12]

The CQ bit was checked by tonyg@chromium.org

[commit-bot: I haz the power, 2014-08-15 22:36:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tonyg@chromium.org/480613002/1

[commit-bot: I haz the power, 2014-08-15 22:36:09]

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

[commit-bot: I haz the power, 2014-08-15 22:36:10]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[tonyg, 2014-08-15 22:36:35]

The CQ bit was checked by tonyg@chromium.org

[commit-bot: I haz the power, 2014-08-15 22:38:35]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tonyg@chromium.org/480613002/1

[dtu, 2014-08-16 00:59:57]

lgtm

[commit-bot: I haz the power, 2014-08-16 07:38:20]

Committed patchset #1 (1) as 290112