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

content/browser/power_profiler/power_profiler_service_unittest.cc

Index: content/browser/power_profiler/power_profiler_service_unittest.cc
diff --git a/content/browser/power_profiler/power_profiler_service_unittest.cc b/content/browser/power_profiler/power_profiler_service_unittest.cc
index 9c4eb21cdfe26246f4d5d33fa35f906c8553e175..f7f77dc82dd6acaa2e60e09636c8c13758a78995 100644
--- a/content/browser/power_profiler/power_profiler_service_unittest.cc
+++ b/content/browser/power_profiler/power_profiler_service_unittest.cc
@@ -13,6 +13,7 @@ namespace content {
 namespace {
 
 const int kNumEvents = 3;
+const int kDefaultSamplePeriodMs = 50;
 
 // Provide a set number of power events.
 class TestPowerDataProvider : public PowerDataProvider {
@@ -35,6 +36,10 @@ class TestPowerDataProvider : public PowerDataProvider {
     return events;
   }
 
+  virtual base::TimeDelta GetSamplingRate() OVERRIDE {
+    return base::TimeDelta::FromMilliseconds(kDefaultSamplePeriodMs);
+  }
+
  private:
   int num_events_to_send_;
   DISALLOW_COPY_AND_ASSIGN(TestPowerDataProvider);