[chromeos] Limit the data samples stored by PowerDataCollector.

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 <vector>
+#include <deque>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
 #include "base/time/time.h"
 #include "chromeos/chromeos_export.h"
 #include "chromeos/dbus/power_manager_client.h"
 
 namespace power_manager {
 class PowerSupplyProperties;
 }
 
 namespace chromeos {
 
@@ skipping 10 matching lines @@
     // 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;
   };
 
-  const std::vector<PowerSupplySnapshot>& power_supply_data() const {
+  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
   // DBusThreadManager is destroyed.
   static void Shutdown();
 
   // Returns the global instance of PowerDataCollector.
   static PowerDataCollector* Get();
 
   // PowerManagerClient::Observer implementation:
   virtual void PowerChanged(
       const power_manager::PowerSupplyProperties& prop) OVERRIDE;
 
+  // Only those power data samples which fall within the last
+  // |kSampleTimeLimitSec| are stored in memory.
+  static const int kSampleTimeLimitSec;
+
  private:
+  FRIEND_TEST_ALL_PREFIXES(PowerDataCollectorTest, AddSnapshot);
+
   PowerDataCollector();
 
   virtual ~PowerDataCollector();
 
-  std::vector<PowerSupplySnapshot> power_supply_data_;
+  // Adds a snapshot to |power_supply_data_|.
+  // It dumps snapshots |kSampleTimeLimitSec| or more older than |snapshot|.
+  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_