Fix android perf bot issue caused by 1550803002

tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor.py

Index: tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor.py
diff --git a/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor.py b/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor.py
index 2a9bd6048acfeb96412a6d99312e3af2dea5d1ad..85e5d30b681341c31ecaa69572280152cdf29109 100644
--- a/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor.py
+++ b/tools/telemetry/telemetry/internal/platform/power_monitor/sysfs_power_monitor.py
@@ -122,6 +122,7 @@ class SysfsPowerMonitor(power_monitor.PowerMonitor):
         logging.warning(
             'Cannot read cpu frequency times for %s due to %s not existing'
             % (cpu, cpu_freq_path))
+        stats[cpu] = None

[Xianzhu, 2015/12/29 19:37:03]

I used another method in https://codereview.chromium.org/1547423002/ because I'm
afraid some 'continue's without setting stats[cpu] in some other methods (e.g.
GetCpuState()) might cause the same issue.

[Yoland Yan(Google), 2015/12/29 19:50:48]

Hmm you are right, I have never seen cpuidle not existing, that's why
GetCpuState() doesn't cause problem for bots. In that case, I will add something
similar in GetCpuState()

         continue
       try:
         stats[cpu] = self._platform.GetFileContents(cpu_freq_path)