content: convert child process notifications to observer usage

content/browser/media/webrtc_internals.h

Index: content/browser/media/webrtc_internals.h
diff --git a/content/browser/media/webrtc_internals.h b/content/browser/media/webrtc_internals.h
index 402b6435aa06cdeabd3f6670efb94ca61987a30c..f466aebe4f53358acc6fb4fe0ac8b35e36130914 100644
--- a/content/browser/media/webrtc_internals.h
+++ b/content/browser/media/webrtc_internals.h
@@ -10,6 +10,7 @@
 #include "base/process.h"
 #include "base/values.h"
 #include "content/common/content_export.h"
+#include "content/public/browser/browser_child_process_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
@@ -20,7 +21,8 @@ class WebRTCInternalsUIObserver;
 // It collects peer connection infomation from the renderers,
 // forwards the data to WebRTCInternalsUIObserver and
 // sends data collecting commands to the renderers.
-class CONTENT_EXPORT WebRTCInternals : public NotificationObserver{
+class CONTENT_EXPORT WebRTCInternals : public BrowserChildProcessObserver,
+                                       public NotificationObserver{
  public:
   static WebRTCInternals* GetInstance();
 
@@ -63,6 +65,10 @@ class CONTENT_EXPORT WebRTCInternals : public NotificationObserver{
   // Sends all update data to the observers.
   void SendAllUpdates();
 
+  // BrowserChildProcessObserver implementation.

[jam, 2013/02/19 18:07:09]

nit: if the methods to implement an interface can be made private, better to do
so so that the public parts of the class is smaller. also move after the
NotificationObserver method

[Paweł Hajdan Jr., 2013/02/20 12:11:42]

Even though I've seen it being done in some parts of the codebase, I don't
remember it being discussed on chromium-dev, and most places don't do that.

Additionally, an "evil" caller could cast to the parent type anyway. See the
following links:
http://stackoverflow.com/questions/484592/overriding-public-virtual-functions...
http://www.parashift.com/c++-faq-lite/hiding-inherited-public.html

If you still consider the above to be blocking this CL, please raise this on
chromium-dev.

[jam, 2013/02/20 19:26:31]

I realize the methods are still reachable through casting. But it makes it more
obvious to developers/reviewers that something weird is happening. These methods
are really implementation details of this class, and as such there's no reason
to expose them in the public section of the class. I consider this good hygiene
(exposing only what's needed).

[Paweł Hajdan Jr., 2013/02/27 19:13:23]

Alright, I've moved things to private when consistent with existing code. I've
tried to make the order of declarations also match the order of inheritance.

Please let me know if there are any remaining issues. For trivial ones, ideally
please give a positive review conditional on fixing these issues.

+  virtual void BrowserChildProcessCrashed(
+      const ChildProcessData& data) OVERRIDE;
+
  private:
   friend struct DefaultSingletonTraits<WebRTCInternals>;
 
@@ -76,6 +82,9 @@ class CONTENT_EXPORT WebRTCInternals : public NotificationObserver{
                        const NotificationSource& source,
                        const NotificationDetails& details) OVERRIDE;
 
+  // Called when a renderer exits (including crashes).
+  void OnRendererExit(int render_process_id);
+
   ObserverList<WebRTCInternalsUIObserver> observers_;
 
   // |peer_connection_data_| is a list containing all the PeerConnection