SystemMonitor refactoring: move power state monitor into a separate class called PowerMonitor

base/power_monitor/power_monitor.cc

Index: base/power_monitor/power_monitor.cc
diff --git a/base/power_monitor/power_monitor.cc b/base/power_monitor/power_monitor.cc
new file mode 100644
index 0000000000000000000000000000000000000000..53c263b5b99f53d08e2548f22b9b296a1752255e
--- /dev/null
+++ b/base/power_monitor/power_monitor.cc
@@ -0,0 +1,118 @@
+// Copyright (c) 2012 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 "base/power_monitor/power_monitor.h"
+
+namespace base {
+
+#if defined(ENABLE_BATTERY_MONITORING)
+// The amount of time (in ms) to wait before running the initial
+// battery check.
+static int kDelayedBatteryCheckMs = 10 * 1000;
+#endif  // defined(ENABLE_BATTERY_MONITORING)
+
+PowerMonitor::PowerMonitor()
+    : observers_(new ObserverListThreadSafe<PowerObserver>()),
+      battery_in_use_(false),
+      suspended_(false),
+      notifier_(NULL)  {
+  DCHECK(MessageLoop::current());
+#if defined(ENABLE_BATTERY_MONITORING)
+  delayed_battery_check_.Start(FROM_HERE,
+      base::TimeDelta::FromMilliseconds(kDelayedBatteryCheckMs), this,
+      &PowerMonitor::BatteryCheck);
+#endif  // defined(ENABLE_BATTERY_MONITORING)
+
+#if defined(OS_MACOSX)
+  PlatformInit();
+#endif
+}
+
+PowerMonitor::~PowerMonitor() {
+#if defined(OS_MACOSX)
+  PlatformDestroy();
+#endif
+}
+
+// static
+PowerMonitor* PowerMonitor::GetInstance() {
+  // The singleton PowerMonitor instance is designed to be leaked since it is
+  // hard to handle the dependency between PowerMonitor and Notifier. We can not
+  // easily anticipate the life time of Notifier after calling GetNotifierOnce.
+  return Singleton<PowerMonitor, LeakySingletonTraits<PowerMonitor> >::get();
+}
+
+PowerMonitor::Notifier* PowerMonitor::GetNotifierOnce() {
+  DCHECK(notifier_ == NULL);
+
+  if (notifier_ == NULL) {
+    // The notifier is allowed to be leaked since the dependency and ownship
+    // between PowerMonitor and Notifier is hard to be handled.
+    notifier_ = new PowerMonitor::Notifier(this);
+    return notifier_;
+  }
+
+  // Return NULL after the first time it get called.
+  return NULL;
+}
+
+void PowerMonitor::AddObserver(PowerObserver* obs) {
+  observers_->AddObserver(obs);
+}
+
+void PowerMonitor::RemoveObserver(PowerObserver* obs) {
+  observers_->RemoveObserver(obs);
+}
+
+void PowerMonitor::ProcessPowerEvent(PowerEvent event_id) {
+  // Suppress duplicate notifications.  Some platforms may
+  // send multiple notifications of the same event.
+  switch (event_id) {
+    case POWER_STATE_EVENT:
+      {
+        bool on_battery = IsBatteryPower();
+        if (on_battery != battery_in_use_) {
+          battery_in_use_ = on_battery;
+          NotifyPowerStateChange();
+        }
+      }
+      break;
+    case RESUME_EVENT:
+      if (suspended_) {
+        suspended_ = false;
+        NotifyResume();
+      }
+      break;
+    case SUSPEND_EVENT:
+      if (!suspended_) {
+        suspended_ = true;
+        NotifySuspend();
+      }
+      break;
+  }
+}
+
+void PowerMonitor::NotifyPowerStateChange() {
+  DVLOG(1) << "PowerStateChange: " << (BatteryPower() ? "On" : "Off")
+           << " battery";
+  observers_->Notify(&PowerObserver::OnPowerStateChange,
+                               BatteryPower());
+}
+
+void PowerMonitor::NotifySuspend() {
+  DVLOG(1) << "Power Suspending";
+  observers_->Notify(&PowerObserver::OnSuspend);
+}
+
+void PowerMonitor::NotifyResume() {
+  DVLOG(1) << "Power Resuming";
+  observers_->Notify(&PowerObserver::OnResume);
+}
+
+void PowerMonitor::BatteryCheck() {
+  ProcessPowerEvent(PowerMonitor::POWER_STATE_EVENT);
+}
+
+}  // namespace base
+