Handle the case freq state data read from file is empty for sysfs_power_montior.

Handle the case freq state data read from file is empty for sysfs_power_montior.

Breakage caused by this case can be found in http://build.chromium.org/p/chromium.perf/builders/Android%20Nexus4%20Perf/builds/1416/steps/page_cycler.bloat/logs/stdio

BUG=

Committed: https://crrev.com/d353816643b2e69c699dfb2c54af460f714c3f25
Cr-Commit-Position: refs/heads/master@{#296861}

[nednguyen, 2014-09-25 23:48:06]

nednguyen@google.com changed reviewers:
+ tonyg@chromium.org

[tonyg, 2014-09-26 00:05:43]

lgtm

https://codereview.chromium.org/610483002/diff/1/tools/telemetry/telemetry/co...
File
tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor.py
(right):

https://codereview.chromium.org/610483002/diff/1/tools/telemetry/telemetry/co...
tools/telemetry/telemetry/core/platform/power_monitor/sysfs_power_monitor.py:161:
if (not initial[cpu]) or (not final[cpu]):
nit: I think we usually prefer to write this w/o the parens.

[nednguyen, 2014-09-26 00:36:17]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2014-09-26 00:37:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/610483002/20001

[commit-bot: I haz the power, 2014-09-26 02:25:24]

Committed patchset #2 (id:20001) as 49b6f8fecceba002dd80766fb5e343a8945b0dbf

[commit-bot: I haz the power, 2014-09-26 02:26:00]

Patchset 2 (id:??) landed as
https://crrev.com/d353816643b2e69c699dfb2c54af460f714c3f25
Cr-Commit-Position: refs/heads/master@{#296861}