--- a/toolkit/modules/BrowserUtils.jsm
+++ b/toolkit/modules/BrowserUtils.jsm
@@ -25,16 +25,22 @@ this.BrowserUtils = {
 
   /**
    * restartApplication: Restarts the application, keeping it in
    * safe mode if it is already in safe mode.
    */
   restartApplication: function() {
     let appStartup = Cc["@mozilla.org/toolkit/app-startup;1"]
                        .getService(Ci.nsIAppStartup);
+    let cancelQuit = Cc["@mozilla.org/supports-PRBool;1"]
+                       .createInstance(Ci.nsISupportsPRBool);
+    Services.obs.notifyObservers(cancelQuit, "quit-application-requested", "restart");
+    if (cancelQuit.data) { // The quit request has been canceled.
+      return false;
+    }
     //if already in safe mode restart in safe mode
     if (Services.appinfo.inSafeMode) {
       appStartup.restartInSafeMode(Ci.nsIAppStartup.eAttemptQuit | Ci.nsIAppStartup.eRestart);
       return;
     }
     appStartup.quit(Ci.nsIAppStartup.eAttemptQuit | Ci.nsIAppStartup.eRestart);
   },