diff --git a/widget/cocoa/nsToolkit.mm b/widget/cocoa/nsToolkit.mm
index 5b63e074fa2..84d97fd3b48 100644
--- a/widget/cocoa/nsToolkit.mm
+++ b/widget/cocoa/nsToolkit.mm
@@ -76,7 +76,7 @@ static void ToolkitSleepWakeCallback(void *refCon, io_service_t service, natural
   {
     case kIOMessageSystemWillSleep:
       // System is going to sleep now.
-      nsToolkit::PostSleepWakeNotification("sleep_notification");
+      nsToolkit::PostSleepWakeNotification(NS_WIDGET_SLEEP_OBSERVER_TOPIC);
       ::IOAllowPowerChange(gRootPort, (long)messageArgument);
       break;
       
@@ -91,7 +91,7 @@ static void ToolkitSleepWakeCallback(void *refCon, io_service_t service, natural
       
     case kIOMessageSystemHasPoweredOn:
       // Handle wakeup.
-      nsToolkit::PostSleepWakeNotification("wake_notification");
+      nsToolkit::PostSleepWakeNotification(NS_WIDGET_WAKE_OBSERVER_TOPIC);
       break;
   }
 
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index 0c1c84500cf..f6f9791827f 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -160,6 +160,29 @@ enum nsTopLevelWidgetZPlacement { // for PlaceBehind()
   eZPlacementTop          // top of the window stack
 };
 
+/**
+ * Before the OS goes to sleep, this topic is notified.
+ */
+#define NS_WIDGET_SLEEP_OBSERVER_TOPIC "sleep_notification"
+
+/**
+ * After the OS wakes up, this topic is notified.
+ */
+#define NS_WIDGET_WAKE_OBSERVER_TOPIC "wake_notification"
+
+/**
+ * Before the OS suspends the current process, this topic is notified.  Some
+ * OS will kill processes that are suspended instead of resuming them.
+ * For that reason this topic may be useful to safely close down resources.
+ */
+#define NS_WIDGET_SUSPEND_PROCESS_OBSERVER_TOPIC "suspend_process_notification"
+
+/**
+ * After the current process resumes from being suspended, this topic is
+ * notified.
+ */
+#define NS_WIDGET_RESUME_PROCESS_OBSERVER_TOPIC "resume_process_notification"
+
 /**
  * Preference for receiving IME updates
  *
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 1f11854f12c..5e64e4a1128 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -5549,7 +5549,8 @@ void nsWindow::PostSleepWakeNotification(const bool aIsSleepMode)
     mozilla::services::GetObserverService();
   if (observerService)
     observerService->NotifyObservers(nullptr,
-      aIsSleepMode ? "sleep_notification" : "wake_notification", nullptr);
+      aIsSleepMode ? NS_WIDGET_SLEEP_OBSERVER_TOPIC :
+                     NS_WIDGET_WAKE_OBSERVER_TOPIC, nullptr);
 }
 
 // RemoveNextCharMessage() should be called by WM_KEYDOWN or WM_SYSKEYDOWM