Adds some debugging code in hopes of identifying a crasher.

content/public/browser/notification_types.h

Index: content/public/browser/notification_types.h
diff --git a/content/public/browser/notification_types.h b/content/public/browser/notification_types.h
index 51c64c3a5e5f292025a1ac59352230fa9cc24ca3..23f947aebb6bb2840dfc1d79d28de15ab6295dc5 100644
--- a/content/public/browser/notification_types.h
+++ b/content/public/browser/notification_types.h
@@ -265,6 +265,11 @@ enum NotificationType {
   // Source<TabContents>.
   NOTIFICATION_TAB_CONTENTS_DESTROYED,
 
+  // This notification is sent when a TabContentsDelegate is being
+  // destroyed. The source is a Source<TabContentsDelegate>.
+  // TODO(sky): Remove when we figure out http://crbug.com/107172.
+  NOTIFICATION_TAB_CONTENTS_DELEGATE_DESTROYED,
+
   // A RenderViewHost was created for a TabContents. The source is the
   // associated TabContents, and the details is the RenderViewHost
   // pointer.