New test fixture for DeviceMotionEventPump to avoid PlatformThread::Sleep

New test fixture for DeviceMotionEventPump to avoid PlatformThread::Sleep

Implement a test fixture in DeviceMotionEventPumpTest to consistently
test DeviceMotionEventPump. The new implementation also avoids calls
to PlatformThread::Sleep() since it is generally undesirable in tests.

BUG=333928
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=245286

[Michael van Ouwerkerk, 2014-01-13 15:17:25]

lgtm

[commit-bot: I haz the power, 2014-01-16 13:55:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/timvolodine@chromium.org/134073002/60001

[commit-bot: I haz the power, 2014-01-16 15:31:13]

Retried try job too often on win_rel for step(s) content_unittests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2014-01-16 15:43:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/timvolodine@chromium.org/134073002/60001

[commit-bot: I haz the power, 2014-01-16 18:02:32]

Retried try job too often on win_rel for step(s) content_unittests,
nacl_integration, sync_integration_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2014-01-16 18:05:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/timvolodine@chromium.org/134073002/60001

[commit-bot: I haz the power, 2014-01-16 19:41:30]

Change committed as 245286