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

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index d2734a57b922726cefc5986e982cad8b6d9a83be..0994b60ee189853db260514479fc28e5e963d971 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -8,7 +8,7 @@
 #include <shellapi.h>
 
 #include "base/bind.h"
-#include "base/system_monitor/system_monitor.h"
+#include "base/power_monitor/power_monitor.h"
 #include "base/win/windows_version.h"
 #include "ui/base/events/event.h"
 #include "ui/base/keycodes/keyboard_code_conversion_win.h"
@@ -1852,9 +1852,8 @@ void HWNDMessageHandler::OnPaint(HDC dc) {
 }
 
 LRESULT HWNDMessageHandler::OnPowerBroadcast(DWORD power_event, DWORD data) {
-  base::SystemMonitor* monitor = base::SystemMonitor::Get();
-  if (monitor)
-    monitor->ProcessWmPowerBroadcastMessage(power_event);
+  base::PowerMonitor* monitor = base::PowerMonitor::GetInstance();
+  monitor->ProcessWmPowerBroadcastMessage(power_event);
   SetMsgHandled(FALSE);
   return 0;
 }