Replace base::CallbackList with base::ObserverList in CastConfigDelegate

ash/system/cast/tray_cast.h

Index: ash/system/cast/tray_cast.h
diff --git a/ash/system/cast/tray_cast.h b/ash/system/cast/tray_cast.h
index a14877702bb068011aea6e6a9a0344bde1d931a5..2137fc0f05fc9ad6eb8a20d607ff07ddec2b7014 100644
--- a/ash/system/cast/tray_cast.h
+++ b/ash/system/cast/tray_cast.h
@@ -9,7 +9,6 @@
 #include "ash/shell_observer.h"
 #include "ash/system/tray/system_tray_item.h"
 #include "base/macros.h"
-#include "base/memory/weak_ptr.h"
 
 namespace ash {
 namespace tray {
@@ -19,7 +18,9 @@ class CastDetailedView;
 class CastDuplexView;
 }  // namespace tray
 
-class ASH_EXPORT TrayCast : public SystemTrayItem, public ShellObserver {
+class ASH_EXPORT TrayCast : public SystemTrayItem,
+                            public ShellObserver,
+                            public CastConfigDelegate::Observer {
  public:
   explicit TrayCast(SystemTray* system_tray);
   ~TrayCast() override;
@@ -50,10 +51,9 @@ class ASH_EXPORT TrayCast : public SystemTrayItem, public ShellObserver {
   // Returns true if the cast extension was detected.
   bool HasCastExtension();
 
-  // Callback used to enable/disable the begin casting view depending on
-  // if we have any cast receivers.
-  void OnReceiversUpdated(
-      const CastConfigDelegate::ReceiversAndActivities& receivers_activities);
+  // Overridden from CastConfigDelegate::Observer.

[achuithb, 2016/01/13 09:21:25]

Maybe move this to after OnCastingSessionStartedOrStopped so all the overrides
are together?

[jdufault, 2016/01/13 19:43:26]

Done.

+  void OnDevicesUpdated(
+      const CastConfigDelegate::ReceiversAndActivities& devices) override;
 
   // This makes sure that the current view displayed in the tray is the correct
   // one, depending on if we are currently casting. If we're casting, then a
@@ -63,16 +63,15 @@ class ASH_EXPORT TrayCast : public SystemTrayItem, public ShellObserver {
   void UpdatePrimaryView();
 
   CastConfigDelegate::ReceiversAndActivities receivers_and_activities_;
-  CastConfigDelegate::DeviceUpdateSubscription device_update_subscription_;
   bool is_casting_ = false;
 
+  bool added_observer_ = false;
+
   // Not owned.
   tray::CastTrayView* tray_ = nullptr;
   tray::CastDuplexView* default_ = nullptr;
   tray::CastDetailedView* detailed_ = nullptr;
 
-  base::WeakPtrFactory<TrayCast> weak_ptr_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(TrayCast);
 };