Cleanup TrayCast with media-router only support in mind.

ash/test/tray_cast_test_api.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/test/tray_cast_test_api.h"
 
 #include "ash/common/cast_config_delegate.h"
 #include "ash/common/system/tray/system_tray.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/wm_shell.h"
@@ skipping 31 matching lines @@
 
 void TrayCastTestAPI::StopCast() {
   return tray_cast_->StopCastForTest();
 }
 
 void TrayCastTestAPI::OnCastingSessionStartedOrStopped(bool is_casting) {
   tray_cast_->OnCastingSessionStartedOrStopped(is_casting);
 }
 
 void TrayCastTestAPI::ReleaseConfigCallbacks() {
-  tray_cast_->added_observer_ = false;
-
   if (WmShell::Get() && WmShell::Get()->system_tray_delegate()) {
     WmShell::Get()
         ->system_tray_delegate()
         ->GetCastConfigDelegate()
         ->RemoveObserver(tray_cast_);
   }
 }
 
 bool TrayCastTestAPI::IsViewDrawn(TrayCast::ChildViewId id) const {
   const views::View* view = tray_cast_->GetDefaultView()->GetViewByID(id);
   return view != nullptr && view->IsDrawn();
 }
 
 }  // namespace ash