Minimize the delegate dependencies for non persistent notifications.

content/public/browser/notification_event_dispatcher.h

Index: content/public/browser/notification_event_dispatcher.h
diff --git a/content/public/browser/notification_event_dispatcher.h b/content/public/browser/notification_event_dispatcher.h
index ce2261b3044b878d67a1110329b87ce2ecf792f5..3a4ce62ba39fbab3febf360f1ba5bee91cb37924 100644
--- a/content/public/browser/notification_event_dispatcher.h
+++ b/content/public/browser/notification_event_dispatcher.h
@@ -56,6 +56,25 @@ class CONTENT_EXPORT NotificationEventDispatcher {
       const NotificationDispatchCompleteCallback&
           dispatch_complete_callback) = 0;
 
+  // Register the renderer process that requested a notification with
+  // |notification_id| to be displayed.
+  virtual void RegisterNonPersistentNotification(
+      const std::string& notification_id,
+      int renderer_id,
+      int non_persistent_id) = 0;

[Peter Beverloo, 2017/05/31 17:52:43]

We should only define methods in the //content/public/ directory that will be
used by consumers outside of //content.

Both RegisterNonPersistentNotification and RendererGone are solely called by the
NotificationMessageFilter, so they can live in NotificationEventDispatcherImpl
(which has a GetInstance() method of its own).

[Miguel Garcia, 2017/06/01 17:00:54]

Done.

+
+  // Dispatch methods for the different notification events.

[Peter Beverloo, 2017/05/31 17:52:43]

Please explain why these are different from the ones above. (I.e. what
"non-persistent" means.)

[Miguel Garcia, 2017/06/01 17:00:54]

Done.

+  virtual void DispatchNonPersistentShowEvent(
+      const std::string& notification_id) = 0;
+  virtual void DispatchNonPersistentClickEvent(
+      const std::string& notification_id) = 0;
+  virtual void DispatchNonPersistentCloseEvent(
+      const std::string& notification_id) = 0;
+
+  // Called when a renderer previously used to display notifications
+  // terminates.
+  virtual void RendererGone(int renderer_id) = 0;

[Peter Beverloo, 2017/05/31 17:52:43]

nit: DidShutdownRenderer()

We're already super late in the process by the time we call this...

[Miguel Garcia, 2017/06/01 17:00:54]

Sure, it cleans up state on the browser when the renderers are gone. Is it a
problem it's called very late in the renderer destruction process?

+
  protected:
   virtual ~NotificationEventDispatcher() {}
 };