Created multi-process-friendly PowerMonitor interface.

base/power_monitor/power_monitor_source.cc

+// 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.
+
+#include "base/power_monitor/power_monitor_source.h"
+
+#include "base/power_monitor/power_monitor.h"
+
+namespace base {
+
+PowerMonitorSource::PowerMonitorSource()
+    : on_battery_power_(false),
+      suspended_(false) {
+}
+
+PowerMonitorSource::~PowerMonitorSource() {
+}
+
+bool PowerMonitorSource::IsOnBatteryPower() {
+  AutoLock auto_lock(lock_);
+  return on_battery_power_;
+}
+
+void PowerMonitorSource::ProcessPowerEvent(PowerEvent event_id) {
+  PowerMonitor* monitor = PowerMonitor::Get();
+  if (!monitor)
+    return;
+
+  PowerMonitorSource* source = monitor->Source();
+
+  // Suppress duplicate notifications.  Some platforms may
+  // send multiple notifications of the same event.
+  switch (event_id) {
+    case POWER_STATE_EVENT:
+      {
+        bool new_on_battery_power = source->IsOnBatteryPowerImpl();
+        bool changed = false;
+
+        source->lock_.Acquire();

[piman, 2013/07/15 20:51:30]

nit: if you want, it's a common pattern to create a scope and use an autolock:

{
  AutoLock lock(source->lock_);
  if (source->on_battery_power_ != new_on_battery_power) {
    changed = true;
    source->on_battery_power_ = new_on_battery_power;
  }
}

+        if (source->on_battery_power_ != new_on_battery_power) {
+            changed = true;
+            source->on_battery_power_ = new_on_battery_power;
+        }
+        source->lock_.Release();
+
+        if (changed)
+          monitor->NotifyPowerStateChange(new_on_battery_power);
+      }
+      break;
+    case RESUME_EVENT:
+      if (source->suspended_) {
+        source->suspended_ = false;
+        monitor->NotifyResume();
+      }
+      break;
+    case SUSPEND_EVENT:
+      if (!source->suspended_) {
+        source->suspended_ = true;
+        monitor->NotifySuspend();
+      }
+      break;
+  }
+}
+
+}  // namespace base