[PowerProfiler] Power Profiler service should detect the sampling rate from the data provider.

content/browser/power_profiler/power_data_provider.h

Index: content/browser/power_profiler/power_data_provider.h
diff --git a/content/browser/power_profiler/power_data_provider.h b/content/browser/power_profiler/power_data_provider.h
index f6c043811f016479cfacc53ff05150fe25e116ec..5c8279f3704f8a93dfbbcf71c28ef3e8c1b2c19e 100644
--- a/content/browser/power_profiler/power_data_provider.h
+++ b/content/browser/power_profiler/power_data_provider.h
@@ -24,6 +24,9 @@ class PowerDataProvider {
 
   // Returns a vector of power events, one per type, for the types it supports.
   virtual PowerEventVector GetData() = 0;
+
+  // Returns sampling rate at which the provider can operate in milliseconds
+  virtual int64 SamplingRate() = 0;

[sky, 2014/06/03 15:41:01]

How about:
virtual base::TimeDelta GetSamplingRate() const = 0;

This way you don't have to document it's in milliseconds as return value is self
documenting. And GetFoo is consistent with similar other code (say on line 26
above).

[vivekg, 2014/06/04 04:35:45]

Done. Yes it makes sense to return the TimeDelta instead of a number. Thanks for
the review.

 };
 
 }  // namespace content