[linux] Avoid crash when there's an X error during shutdown.

chrome/browser/ui/browser_list.cc

Index: chrome/browser/ui/browser_list.cc
diff --git a/chrome/browser/ui/browser_list.cc b/chrome/browser/ui/browser_list.cc
index 08a9d1dd07fc57bead857c04353f26aa46d16c45..8c7c1728c021f3f5cb810f4fd724a75f5823638d 100644
--- a/chrome/browser/ui/browser_list.cc
+++ b/chrome/browser/ui/browser_list.cc
@@ -393,7 +393,9 @@ void BrowserList::CloseAllBrowsersAndExit() {
 void BrowserList::SessionEnding() {
   // EndSession is invoked once per frame. Only do something the first time.
   static bool already_ended = false;
-  if (already_ended)
+  // We may get called in the middle of shutdown, e.g. http://crbug.com/70852
+  // In this case, do nothing.
+  if (already_ended || !NotificationService::current())
     return;
   already_ended = true;