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

content/browser/power_profiler/power_data_provider_ia_win.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/power_profiler/power_data_provider_ia_win.h"
 
+#include "base/basictypes.h"
 #include "base/logging.h"
 
 namespace content {
 
+// Default sampling period, as recommended by Intel Power Gadget.
+// Section 3.1 of
+// http://software.intel.com/en-us/blogs/2013/10/03/using-the-intel-power-gadget-api-on-windows
+const int kDefaultSamplePeriodMs = 50;
+
 scoped_ptr<PowerDataProvider> PowerDataProvider::Create() {
   scoped_ptr<PowerDataProviderIA> provider(new PowerDataProviderIA());
   if (provider->Initialize())
     return make_scoped_ptr<PowerDataProvider>(provider.release());
 
   return make_scoped_ptr<PowerDataProvider>(NULL);
 }
 
 PowerDataProviderIA::PowerDataProviderIA()
     : sockets_number_(0),
@@ skipping 26 matching lines @@
   }
 
   event.type = PowerEvent::SOC_PACKAGE;
   event.value = package_power;
   event.time = base::TimeTicks::Now();
   events.push_back(event);
 
   return events;
 }
 
+base::TimeDelta PowerDataProviderIA::GetSamplingRate() {
+  return base::TimeDelta::FromMilliseconds(kDefaultSamplePeriodMs);
+}
+
 bool PowerDataProviderIA::Initialize() {
   if (is_open_)
     return true;
 
   if (!energy_lib_.IntelEnergyLibInitialize()) {
     LOG(ERROR) << "Power Data Provider initialize failed!";
     return false;
   }
 
   energy_lib_.GetNumNodes(&sockets_number_);
@@ skipping 14 matching lines @@
 
     if (package_msr_name.compare(name) == 0)
       power_msr_ids_[PowerEvent::SOC_PACKAGE] = i;
   }
 
   is_open_ = true;
   return true;
 }
 
 }  // namespace content