[chromeos] Add a battery discharge rate plot to about:power page.

chromeos/power/power_data_collector.h

 // Copyright 2013 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 CHROMEOS_POWER_POWER_DATA_COLLECTOR_H_
 #define CHROMEOS_POWER_POWER_DATA_COLLECTOR_H_
 
 #include <deque>
 
 #include "base/basictypes.h"
@@ skipping 20 matching lines @@
     PowerSupplySnapshot();
 
     // Time when the snapshot was captured.
     base::TimeTicks time;
 
     // True if connected to external power at the time of the snapshot.
     bool external_power;
 
     // The battery charge as a percentage of full charge in range [0.0, 100.00].
     double battery_percent;
+
+    // The battery discharge rate in W. Positive if the battery is being
+    // discharged and negative if it's being charged.
+    double battery_discharge_rate;
   };
 
   const std::deque<PowerSupplySnapshot>& power_supply_data() const {
     return power_supply_data_;
   }
 
   // Can be called only after DBusThreadManager is initialized.
   static void Initialize();
 
   // Can be called only if initialized via Initialize, and before
@@ skipping 23 matching lines @@
   void AddSnapshot(const PowerSupplySnapshot& snapshot);
 
   std::deque<PowerSupplySnapshot> power_supply_data_;
 
   DISALLOW_COPY_AND_ASSIGN(PowerDataCollector);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_POWER_POWER_DATA_COLLECTOR_H_