Fixes bug where NonClientFrameController wasn't registered correctly

ash/mus/non_client_frame_controller.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/mus/non_client_frame_controller.h"
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
@@ skipping 290 matching lines @@
   params.parent = parent;
   params.context = context;
   // TODO: properly set |params.activatable|. Should key off whether underlying
   // (mus) window can have focus.
   params.delegate = this;
   params.bounds = bounds;
   WmNativeWidgetAura* native_widget = new WmNativeWidgetAura(
       widget_, window_manager_client_, ShouldRemoveStandardFrame(*properties),
       ShouldEnableImmersive(*properties));
   window_ = native_widget->GetNativeView();
+  window_->SetProperty(kNonClientFrameControllerKey, this);
   window_->SetProperty(kWidgetCreationTypeKey, WidgetCreationType::FOR_CLIENT);
   window_->AddObserver(this);
   params.native_widget = native_widget;
   aura::SetWindowType(window_, window_type);
   aura::PropertyConverter* property_converter =
       window_manager->property_converter();
   for (auto& property_pair : *properties) {
     property_converter->SetPropertyFromTransportValue(
         window_, property_pair.first, &property_pair.second);
   }
@@ skipping 128 matching lines @@
   }
 }
 
 void NonClientFrameController::OnWindowDestroyed(aura::Window* window) {
   window_->RemoveObserver(this);
   window_ = nullptr;
 }
 
 }  // namespace mus
 }  // namespace ash