Delete empty NotificationObserverLists. Fixes leak.

content/browser/notification_service_impl.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/notification_service_impl.h"
 
 #include "base/lazy_instance.h"
 #include "base/threading/thread_local.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_types.h"
 
@@ skipping 60 matching lines @@
   // has its deleted pointer in its map.  A garbge object will be called in the
   // future.
   // NOTE: when this check shows crashes, use BrowserThread::DeleteOnIOThread or
   // other variants as the trait on the object.
   CHECK(HasKey(observers_[type], source));
 
   NotificationObserverList* observer_list =
       observers_[type][source.map_key()];
   if (observer_list) {
     observer_list->RemoveObserver(observer);
+    if (!observer_list->size()) {
+      observers_[type].erase(source.map_key());
+      delete observer_list;
+    }
 #ifndef NDEBUG
     --observer_counts_[type];
 #endif
   }
-
-  // TODO(jhughes): Remove observer list from map if empty?
 }
 
 void NotificationServiceImpl::Notify(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   DCHECK(type > content::NOTIFICATION_ALL) <<
       "Allowed for observing, but not posting.";
 
   // There's no particular reason for the order in which the different
@@ skipping 45 matching lines @@
   }
 #endif
 
   for (int i = 0; i < static_cast<int>(observers_.size()); i++) {
     NotificationSourceMap omap = observers_[i];
     for (NotificationSourceMap::iterator it = omap.begin();
          it != omap.end(); ++it)
       delete it->second;
   }
 }