Battery impact UMA

content/browser/power_usage_monitor_impl.h

Index: content/browser/power_usage_monitor_impl.h
diff --git a/content/browser/power_usage_monitor_impl.h b/content/browser/power_usage_monitor_impl.h
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+++ b/content/browser/power_usage_monitor_impl.h
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+// 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 CHROME_CONTENT_BROWSER_POWER_USAGE_MONITOR_IMPL_H_
+#define CHROME_CONTENT_BROWSER_POWER_USAGE_MONITOR_IMPL_H_
+
+#include "base/basictypes.h"
+#include "base/containers/hash_tables.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/singleton.h"
+#include "base/power_monitor/power_monitor.h"
+#include "base/time/time.h"
+#include "content/public/browser/browser_message_filter.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+#include "device/battery/battery_status_service.h"
+
+namespace content {
+
+// Record statistics on power usage.
+//
+// Two main statics are recorded by this class:
+// * Power.BatteryDischarge_{5,15,30} - delta between battery level when
+//   unplugged from wallpower, over the specified period - in minutes.
+// * Power.BatteryDischargeRateWhenUnplugged - the rate of battery discharge
+//   from the device being unplugged until it's plugged back in, if said period
+//   was longer than 30 minutes.
+//
+// Heuristics:
+// * Metrics are only collected once per day.

[Daniel Erat, 2014/11/04 17:04:03]

this is outdated now, right?

[jeremy, 2014/11/05 11:40:19]

Done.

+// * If the machine goes to sleep or all renderers are closed then the current
+//   measurement is cancelled.
+class PowerUsageMonitor : public base::PowerObserver,
+                          public NotificationObserver {
+ public:
+  class SystemInterface {
+   public:
+    virtual ~SystemInterface() {}
+
+    virtual void ScheduleHistogramReport(base::TimeDelta delay) = 0;
+    virtual void CancelPendingHistogramReports() = 0;
+
+    // Allow tests to override clock.
+    virtual base::Time Now() = 0;
+  };
+
+ public:
+  PowerUsageMonitor();
+  virtual ~PowerUsageMonitor();

[Daniel Erat, 2014/11/04 17:04:03]

nit: override instead of virtual

[jeremy, 2014/11/05 11:40:19]

Done.

+
+  // Start monitoring power usage.
+  // Note that the actual monitoring will be delayed until 30 minutes after
+  // system boot.
+  void Start();
+
+  double discharge_amount() {

[Daniel Erat, 2014/11/04 17:04:03]

nit: move above Start() since this is inlined; also make it const

[jeremy, 2014/11/05 11:40:19]

Done.

+    return initial_battery_level_ - current_battery_level_;
+  }
+
+  void SetSystemInterfaceForTest(scoped_ptr<SystemInterface> interface);
+  void SetRenderersForTest(bool has_live_renderers);
+
+  // Overridden from base::PowerObserver:
+  void OnPowerStateChange(bool on_battery_power) override {};

[Daniel Erat, 2014/11/04 17:04:03]

don't inline this and OnResume():
http://www.chromium.org/developers/coding-style/cpp-dos-and-donts#TOC-Stop-in....

[jeremy, 2014/11/05 11:40:19]

Done.

+  void OnResume() override {};
+  void OnSuspend() override;
+
+  // Overridden from NotificationObserver:
+  void Observe(int type,
+               const NotificationSource& source,
+               const NotificationDetails& details) override;
+
+ private:
+  friend class PowerUsageMonitorTest;
+  FRIEND_TEST_ALL_PREFIXES(PowerUsageMonitorTest, OnBatteryStatusUpdate);
+
+  // Start monitoring system power usage.
+  // This function may be called after a delay, see Start() for details.
+  void StartInternal();
+
+  void OnBatteryStatusUpdate(const device::BatteryStatus& status);
+
+  void DischargeStarted(double battery_level);
+  void WallPowerConnected(double battery_level);
+
+  void CancelPendingHistogramReporting();
+
+  device::BatteryStatusService::BatteryUpdateCallback callback_;
+  scoped_ptr<device::BatteryStatusService::BatteryUpdateSubscription>
+      subscription_;
+
+  NotificationRegistrar registrar_;
+
+  scoped_ptr<SystemInterface> system_interface_;
+
+  // True if monitoring was started (Start() called).
+  bool started_;
+
+  // True if the system is running on battery power, false if on wall power.
+  bool on_battery_power_;
+
+  // Battery level when wall power disconnected, 0 if on wall power.
+  // Scale is [0.0, 1.0].
+  double initial_battery_level_;
+
+  // Current battery level, 0 if on wall power.

[Daniel Erat, 2014/11/04 17:04:03]

nit: document the range here (specifically the upper bound)

[jeremy, 2014/11/05 11:40:19]

Done.

+  double current_battery_level_;
+
+  // Timestamp when wall power was disconnected, null Time object otherwise.
+  base::Time start_discharge_time_;
+
+  // IDs of live renderer processes.
+  base::hash_set<int> live_renderer_ids_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PowerUsageMonitor);
+};
+
+}  // namespace content
+
+#endif  // CHROME_CONTENT_BROWSER_POWER_USAGE_MONITOR_IMPL_H_