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

base/power_monitor/power_monitor_mac.mm

Index: base/power_monitor/power_monitor_mac.mm
diff --git a/base/system_monitor/system_monitor_mac.mm b/base/power_monitor/power_monitor_mac.mm
similarity index 81%
rename from base/system_monitor/system_monitor_mac.mm
rename to base/power_monitor/power_monitor_mac.mm
index d0dbaabcd4417864b21166e81c068e20c769cbe6..319776c26faa6f27c9a76a9fbda5979d7947aa8c 100644
--- a/base/system_monitor/system_monitor_mac.mm
+++ b/base/power_monitor/power_monitor_mac.mm
@@ -5,13 +5,19 @@
 // Implementation based on sample code from
 // http://developer.apple.com/library/mac/#qa/qa1340/_index.html.
 
-#include "base/system_monitor/system_monitor.h"
+#include "base/power_monitor/power_monitor.h"
 
 #include <IOKit/pwr_mgt/IOPMLib.h>
 #include <IOKit/IOMessage.h>
 
 namespace base {
 
+// A helper function as a friend function of PowerMonitor.
+void ProcessPowerEventHelper(PowerMonitor::PowerEvent power_event) {
+  PowerMonitor* power_monitor = PowerMonitor::GetInstance();
+  power_monitor->ProcessPowerEvent(power_event);
+}
+
 namespace {
 
 io_connect_t g_system_power_io_port = 0;
@@ -22,17 +28,15 @@ void SystemPowerEventCallback(void*,
                               io_service_t service,
                               natural_t message_type,
                               void* message_argument) {
-  SystemMonitor* sys_monitor = SystemMonitor::Get();
-  DCHECK(sys_monitor);
   switch (message_type) {
     case kIOMessageSystemWillSleep:
-      sys_monitor->ProcessPowerMessage(SystemMonitor::SUSPEND_EVENT);
+      ProcessPowerEventHelper(PowerMonitor::SUSPEND_EVENT);
       IOAllowPowerChange(g_system_power_io_port,
           reinterpret_cast<intptr_t>(message_argument));
       break;
 
     case kIOMessageSystemWillPowerOn:
-      sys_monitor->ProcessPowerMessage(SystemMonitor::RESUME_EVENT);
+      ProcessPowerEventHelper(PowerMonitor::RESUME_EVENT);
       break;
   }
 }
@@ -45,7 +49,7 @@ void SystemPowerEventCallback(void*,
 // See crbug.com/83783 .
 
 // static
-void SystemMonitor::AllocateSystemIOPorts() {
+void PowerMonitor::AllocateSystemIOPorts() {
   DCHECK_EQ(g_system_power_io_port, 0u);
 
   // Notification port allocated by IORegisterForSystemPower.
@@ -57,8 +61,8 @@ void SystemMonitor::AllocateSystemIOPorts() {
   DCHECK_NE(g_system_power_io_port, 0u);
 }
 
-void SystemMonitor::PlatformInit() {
-  // Need to call AllocateSystemIOPorts() before constructing a SystemMonitor
+void PowerMonitor::PlatformInit() {
+  // Need to call AllocateSystemIOPorts() before creating a PowerMonitor
   // object.
   DCHECK_NE(g_system_power_io_port, 0u);
   if (g_system_power_io_port == 0)
@@ -71,7 +75,8 @@ void SystemMonitor::PlatformInit() {
       kCFRunLoopCommonModes);
 }
 
-void SystemMonitor::PlatformDestroy() {
+
+void PowerMonitor::PlatformDestroy() {
   DCHECK_NE(g_system_power_io_port, 0u);
   if (g_system_power_io_port == 0)
     return;