[Android] Support idle wakeup measurement with /proc/timer_stats

tools/perf/metrics/power.py

Index: tools/perf/metrics/power.py
diff --git a/tools/perf/metrics/power.py b/tools/perf/metrics/power.py
index 596bfd818c54a2975fdc21ff662cb6d35598c3b0..ff9bd1278843abe2beda3d44c1ff143601c2dc53 100644
--- a/tools/perf/metrics/power.py
+++ b/tools/perf/metrics/power.py
@@ -70,6 +70,9 @@ class PowerMetric(Metric):
   def Start(self, _, tab):
     self._browser = tab.browser
 
+    if self._platform.CanMeasureIdleWakeUps():
+      self._platform.StartMeasuringIdleWakeUps()
+
     if not self._platform.CanMonitorPower():
       return
 
@@ -77,11 +80,17 @@ class PowerMetric(Metric):
     self._StopInternal()
 
     # This line invokes top a few times, call before starting power measurement.
+    # TODO(jdduke): Move idle wakeup measurement into standalone PowerMonitor
+    # instances. Including wakeups in the "instantaneous" CPU stats object is
+    # awkward on Linux-based platforms.
     self._starting_cpu_stats = self._browser.cpu_stats
     self._platform.StartMonitoringPower(self._browser)
     self._running = True
 
   def Stop(self, _, tab):
+    if self._platform.CanMeasureIdleWakeUps():
+      self._platform.StopMeasuringIdleWakeUps()
+
     if not self._platform.CanMonitorPower():
       return