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 0b53dc97dee0c242bc5aafa3ffb368b585cb051f..a94c6a90088953305290e7634c4e474a7c54c671 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"
@@ -40,6 +40,9 @@
 namespace views {
 namespace {
 
+// Reference the Signaler defined in the global PowerMonitor instance.

[vandebo (ex-Chrome), 2012/10/29 18:04:38]

Remove or update this comment to say *why* this is here.

[Hongbo Min, 2012/10/30 14:33:47]

Done.

+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
@@ -385,6 +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() {
@@ -1847,9 +1852,9 @@ 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);
+  CHECK(!g_power_signaler);
+  g_power_signaler->ProcessWmPowerBroadcastMessage(power_event);
+
   SetMsgHandled(FALSE);
   return 0;
 }