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 0312549e2aae88dd43c2c2ff5c6bdf67561b5610..a90a55cfe5077daf08ca6697aade78b389537108 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"
@@ -39,6 +39,10 @@
 namespace views {
 namespace {
 
+// Used to signal the power event when receiving Windows power broadcast
+// message.
+base::PowerMonitor::Signaler* g_power_signaler = NULL;
+
 // MoveLoopMouseWatcher is used to determine if the user canceled or completed a
 // move. win32 doesn't appear to offer a way to determine the result of a move,
 // so we install hooks to determine if we got a mouse up and assume the move
@@ -384,6 +388,8 @@ HWNDMessageHandler::HWNDMessageHandler(HWNDMessageHandlerDelegate* delegate)
       layered_alpha_(255),
       ALLOW_THIS_IN_INITIALIZER_LIST(paint_layered_window_factory_(this)),
       can_update_layered_window_(true) {
+  if (g_power_signaler == NULL && base::PowerMonitor::Get())
+    g_power_signaler = base::PowerMonitor::Get()->GetSignalerOnce();
 }
 
 HWNDMessageHandler::~HWNDMessageHandler() {
@@ -393,6 +399,8 @@ HWNDMessageHandler::~HWNDMessageHandler() {
   // Prevent calls back into this class via WNDPROC now that we've been
   // destroyed.
   ClearUserData();
+  delete g_power_signaler;
+  g_power_signaler = NULL;
 }
 
 void HWNDMessageHandler::Init(HWND parent, const gfx::Rect& bounds) {
@@ -1846,9 +1854,11 @@ 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);
+  if (base::PowerMonitor::Get()) {
+    CHECK(g_power_signaler);
+    g_power_signaler->ProcessWmPowerBroadcastMessage(power_event);
+  }
+
   SetMsgHandled(FALSE);
   return 0;
 }