[Telemetry] Fix idle wakeup reporting in the face of dead processes

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 c871b1dd9fc908fdb3a0cd8eb44908cf802c75cb..cc55d470d27491ac64d5a2a7bc46603fda5f2fd8 100644
--- a/tools/perf/metrics/power.py
+++ b/tools/perf/metrics/power.py
@@ -5,6 +5,7 @@
 import time
 
 from metrics import Metric
+from telemetry.core.platform import timeline_objects
 from telemetry.value import scalar
 
 
@@ -178,7 +179,12 @@ def _SubtractCpuStats(cpu_stats, start_cpu_stats):
     if (('IdleWakeupCount' not in cpu_stats[process_type]) or
         ('IdleWakeupCount' not in start_cpu_stats[process_type])):
       continue
+
+    # Verify that the IdleWakeupCount field has been converted to a

[tonyg, 2014/08/24 16:53:43]

Let's just kill this comment. It answers "what" instead of "why" which is
usually extraneous.

[jeremy, 2014/08/26 14:14:16]

Done.

+    # TimlineData-based object.
+    assert isinstance(cpu_stats[process_type]['IdleWakeupCount'],
+        timeline_objects.IdleStatsData)
     idle_wakeup_delta = (cpu_stats[process_type]['IdleWakeupCount'] -
                         start_cpu_stats[process_type]['IdleWakeupCount'])
-    cpu_delta[process_type] = idle_wakeup_delta
+    cpu_delta[process_type] = idle_wakeup_delta.IdleWakeupCount()
   return cpu_delta