Add a CHECK when an object tries to remove itself as an observer from Notific...

chrome/common/notification_service.cc

Index: chrome/common/notification_service.cc
===================================================================
--- chrome/common/notification_service.cc	(revision 30793)
+++ chrome/common/notification_service.cc	(working copy)
@@ -60,8 +60,15 @@
                                          NotificationType type,
                                          const NotificationSource& source) {
   DCHECK(type.value < NotificationType::NOTIFICATION_TYPE_COUNT);
-  DCHECK(HasKey(observers_[type.value], source));
 
+  // This is a very serious bug.  An object is most likely being deleted on
+  // the wrong thread, and as a result another thread's NotificationService
+  // has its deleted pointer in its map.  A garbge object will be called in the
+  // future.
+  // NOTE: when this check shows crashes, use ChromeThread::DeleteOnIOThread or
+  // other variants as the trait on the object.
+  CHECK(HasKey(observers_[type.value], source));
+
   NotificationObserverList* observer_list =
       observers_[type.value][source.map_key()];
   if (observer_list) {