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

content/browser/power_profiler/power_data_provider_ia_win.h

 // 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.
 
 #ifndef CONTENT_BROWSER_POWER_PROFILER_POWER_DATA_PROVIDER_IA_WIN_H_
 #define CONTENT_BROWSER_POWER_PROFILER_POWER_DATA_PROVIDER_IA_WIN_H_
 
 #include "base/basictypes.h"
 #include "content/browser/power_profiler/power_data_provider.h"
 #include "third_party/power_gadget/PowerGadgetLib.h"
 
 namespace content {
 
 // A class used to get power usage via Power Gadget API.
 class PowerDataProviderIA : public PowerDataProvider {
  public:
   PowerDataProviderIA();
 
   virtual ~PowerDataProviderIA();
 
   bool Initialize();
   virtual PowerEventVector GetData() OVERRIDE;
+  virtual int64 SamplingRate() OVERRIDE;
 
  private:
   CIntelPowerGadgetLib energy_lib_;
 
   int sockets_number_;
   int power_msr_ids_[PowerEvent::ID_COUNT];
   bool is_open_;
   DISALLOW_COPY_AND_ASSIGN(PowerDataProviderIA);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_POWER_PROFILER_POWER_DATA_PROVIDER_IA_WIN_H_