Simplify BrowserChildProcessHost in preparation for refactoring it so that consumers embed it in ...

content/public/browser/notification_types.h

Index: content/public/browser/notification_types.h
===================================================================
--- content/public/browser/notification_types.h	(revision 112769)
+++ content/public/browser/notification_types.h	(working copy)
@@ -391,13 +391,6 @@
   // a Details<content::ChildProcessData>.
   NOTIFICATION_CHILD_PROCESS_CRASHED,
 
-  // This message is sent when a child process disappears
-  // unexpectedly as a result of a termination signal.  There is no
-  // usable source, since it is sent from an ephemeral task;
-  // register for AllSources() to receive this notification.  The
-  // details are in a Details<content::ChildProcessData>.
-  NOTIFICATION_CHILD_PROCESS_WAS_KILLED,
-
   // This message indicates that an instance of a particular child was
   // created in a page.  (If one page contains several regions rendered by
   // the same child, this notification will occur once for each region