Add forwarding comments to obsolete notifications.

BUG=357627

Change-Id: I62ff9157d6d41bd4581ba3d080dca2c309cb3e82
Reviewed-on: https://chromium-review.googlesource.com/978387Reviewed-by: Sidney San Martín <sdy@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545564}

content/public/browser/notification_types.h

@@ -96,16 +96,19 @@ enum NotificationType {
   // Indicates that a RenderProcessHost was created and its handle is now
   // available. The source will be the RenderProcessHost that corresponds to
   // the process.
+  // DEPRECATED: Use RenderProcessHostObserver::RenderProcessReady()
   NOTIFICATION_RENDERER_PROCESS_CREATED,
 
   // Indicates that a RenderProcessHost is destructing. The source will be the
   // RenderProcessHost that corresponds to the process.
+  // DEPRECATED: Use RenderProcessHostObserver::RenderProcessHostDestroyed()
   NOTIFICATION_RENDERER_PROCESS_TERMINATED,
 
   // Indicates that a render process was closed (meaning it exited, but the
   // RenderProcessHost might be reused).  The source will be the corresponding
   // RenderProcessHost.  The details will be a RendererClosedDetails struct.
   // This may get sent along with RENDERER_PROCESS_TERMINATED.
+  // DEPRECATED: Use RenderProcessHostObserver::RenderProcessExited()
   NOTIFICATION_RENDERER_PROCESS_CLOSED,
 
   // Indicates that a RenderWidgetHost has become unresponsive for a period of