content: Remove usage of NOTIFICATION_WEB_CONTENTS_DESTROYED from content

content/shell/shell.h

Index: content/shell/shell.h
diff --git a/content/shell/shell.h b/content/shell/shell.h
index 852cd0f8d6bae810ed8d99163eee179861cf4a24..a92876e7e82da0a5bcdc38a69e358111e5767d2d 100644
--- a/content/shell/shell.h
+++ b/content/shell/shell.h
@@ -14,6 +14,7 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_delegate.h"
+#include "content/public/browser/web_contents_observer.h"
 #include "ipc/ipc_channel.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/size.h"
@@ -49,6 +50,7 @@ class WebContents;
 // This represents one window of the Content Shell, i.e. all the UI including
 // buttons and url bar, as well as the web content area.
 class Shell : public WebContentsDelegate,
+              public WebContentsObserver,

[jochen (gone - plz use gerrit), 2013/05/10 19:53:33]

Shell shouldn't be a WebContentsObserver. Can you use a similar destruction
observer patterns as you use in WCI?

[Avi (use Gerrit), 2013/05/10 20:26:44]

What's your reasoning here?

[Paweł Hajdan Jr., 2013/05/13 20:15:31]

Done.

[Avi (use Gerrit), 2013/05/15 19:22:19]

Jochen: I will again ask why. Shell needs to observe a single WC, so why this
game of indirection and a proxy object?

[jochen (gone - plz use gerrit), 2013/05/21 12:09:44]

As I said, I don't remember the discussion we had about this exactly. In
general, Shell is a pretty lame object - a concept like this doesn't exist at
all in chrome/. It's a bit like a bastardized TabContents before we deleted it.

I think we should delete Shell all together (just like we did with TabContents).
Making it implement both WebContentsDelegate and WebContentsObserver will make
it just more difficult.

               public NotificationObserver {
  public:
   virtual ~Shell();
@@ -143,6 +145,9 @@ class Shell : public WebContentsDelegate,
   virtual void ActivateContents(WebContents* contents) OVERRIDE;
   virtual void DeactivateContents(WebContents* contents) OVERRIDE;
 
+  // WebContentsObserver
+  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
+
  private:
   enum UIControl {
     BACK_BUTTON,