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

ash/test/tray_cast_test_api.cc

Index: ash/test/tray_cast_test_api.cc
diff --git a/ash/test/tray_cast_test_api.cc b/ash/test/tray_cast_test_api.cc
index 5d0bcf8aab277930581d87407e18bcec6a98b317..90a0aeb13c4122808cc7f2c27b3a7ff4da99435c 100644
--- a/ash/test/tray_cast_test_api.cc
+++ b/ash/test/tray_cast_test_api.cc
@@ -4,7 +4,10 @@
 
 #include "ash/test/tray_cast_test_api.h"
 
+#include "ash/cast_config_delegate.h"
+#include "ash/shell.h"
 #include "ash/system/tray/system_tray.h"
+#include "ash/system/tray/system_tray_delegate.h"
 #include "ui/views/view.h"
 
 namespace ash {
@@ -46,7 +49,15 @@ void TrayCastTestAPI::OnCastingSessionStartedOrStopped(bool is_casting) {
 }
 
 void TrayCastTestAPI::ReleaseConfigCallbacks() {
-  tray_cast_->device_update_subscription_.reset();
+  tray_cast_->added_observer_ = false;
+
+  if (ash::Shell::GetInstance() &&
+      ash::Shell::GetInstance()->system_tray_delegate()) {
+    ash::Shell::GetInstance()
+        ->system_tray_delegate()
+        ->GetCastConfigDelegate()
+        ->RemoveObserver(tray_cast_);
+  }
 }
 
 bool TrayCastTestAPI::IsViewDrawn(TrayCast::ChildViewId id) const {