Use WmLayoutManager::OnChildWindowVisibilityChanged to update the system modal state.

ash/wm/system_modal_container_layout_manager_unittest.cc

 // Copyright (c) 2012 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/common/wm/system_modal_container_layout_manager.h"
 
 #include <memory>
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/session/session_state_delegate.h"
@@ skipping 766 matching lines @@
           ->GetPrimaryRootWindowController()
           ->GetSystemModalLayoutManager(WmWindowAura::Get(modal_window.get()));
 
   EXPECT_FALSE(WmShell::Get()->IsSystemModalWindowOpen());
   EXPECT_FALSE(layout_manager->has_window_dimmer());
 
   modal_window->Show();
   EXPECT_TRUE(WmShell::Get()->IsSystemModalWindowOpen());
   EXPECT_TRUE(layout_manager->has_window_dimmer());
 
+  // Make sure that a child visibility change should not cause
+  // inconsistent state.
+  std::unique_ptr<aura::Window> child(new aura::Window(nullptr));

[sky, 2016/09/27 22:10:57]

MakeUnique rather than new.

[oshima, 2016/09/28 14:26:00]

Done.

+  child->SetType(ui::wm::WINDOW_TYPE_CONTROL);
+  child->Init(ui::LAYER_TEXTURED);
+  modal_window->AddChild(child.get());
+  child->Show();
+  EXPECT_TRUE(WmShell::Get()->IsSystemModalWindowOpen());
+  EXPECT_TRUE(layout_manager->has_window_dimmer());
+
   modal_window->Hide();
   EXPECT_FALSE(WmShell::Get()->IsSystemModalWindowOpen());
   EXPECT_FALSE(layout_manager->has_window_dimmer());
 
   modal_window->Show();
   EXPECT_TRUE(WmShell::Get()->IsSystemModalWindowOpen());
   EXPECT_TRUE(layout_manager->has_window_dimmer());
 }
 
 namespace {
@@ skipping 90 matching lines @@
   if (!SupportsMultipleDisplays())
     return;
 
   UpdateDisplay("500x500, 500x500");
   InputTestDelegate delegate;
   delegate.RunTest(this);
 }
 
 }  // namespace test
 }  // namespace ash