Gets mash to use WmToplevelWindowEventHandler

mash/wm/shelf_layout_manager.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 "mash/wm/shelf_layout_manager.h"
 
 #include "components/mus/public/cpp/window.h"
 #include "mash/wm/property_util.h"
 #include "mash/wm/public/interfaces/ash_window_type.mojom.h"
 #include "ui/gfx/geometry/rect.h"
@@ skipping 17 matching lines @@
   }
   return nullptr;
 }
 
 // We explicitly don't make assertions about the number of children in this
 // layout as the number of children can vary when the application providing the
 // shelf restarts.
 
 void ShelfLayoutManager::LayoutWindow(mus::Window* window) {
   if (GetAshWindowType(window) != mojom::AshWindowType::SHELF) {
-    NOTREACHED() << "Unknown window in USER_SHELF container.";
+    // Phantom windows end up in this container, ignore them.
     return;
   }
   gfx::Size size = GetWindowPreferredSize(window);
 
   if (alignment_ == shelf::mojom::Alignment::BOTTOM) {
     const int y = owner()->bounds().height() - size.height();
     size.set_width(owner()->bounds().width());
     window->SetBounds(gfx::Rect(0, y, size.width(), size.height()));
   } else {
     const int x = (alignment_ == shelf::mojom::Alignment::LEFT)
@@ skipping 17 matching lines @@
     shelf::mojom::AutoHideBehavior auto_hide) {
   if (auto_hide_behavior_ == auto_hide)
     return;
 
   auto_hide_behavior_ = auto_hide;
   NOTIMPLEMENTED();
 }
 
 }  // namespace wm
 }  // namespace mash