Add system modals to the proper container in mus+ash.

services/ui/test_wm/test_wm.cc

 // Copyright 2016 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 <memory>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "mojo/public/cpp/bindings/binding.h"
@@ skipping 90 matching lines @@
   bool OnWmSetBounds(aura::Window* window, gfx::Rect* bounds) override {
     window->SetBounds(*bounds);
     return true;
   }
   bool OnWmSetProperty(
       aura::Window* window,
       const std::string& name,
       std::unique_ptr<std::vector<uint8_t>>* new_data) override {
     return true;
   }
+  void OnWmSetModalType(aura::Window* window, ui::ModalType type) override {}
   void OnWmSetCanFocus(aura::Window* window, bool can_focus) override {}
   aura::Window* OnWmCreateTopLevelWindow(
       ui::mojom::WindowType window_type,
       std::map<std::string, std::vector<uint8_t>>* properties) override {
     aura::Window* window = new aura::Window(nullptr);
     SetWindowType(window, window_type);
     window->Init(LAYER_NOT_DRAWN);
     window->SetBounds(gfx::Rect(10, 10, 500, 500));
     root_->AddChild(window);
     return window;
@@ skipping 69 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(TestWM);
 };
 
 }  // namespace test
 }  // namespace ui
 
 MojoResult ServiceMain(MojoHandle service_request_handle) {
   service_manager::ServiceRunner runner(new ui::test::TestWM);
   return runner.Run(service_request_handle);
 }