mash: Create and show a shelf in mash.

ash/common/shelf/shelf_window_watcher.cc

 // Copyright 2013 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/shelf/shelf_window_watcher.h"
 
 #include <memory>
 #include <utility>
 
 #include "ash/common/shelf/shelf_constants.h"
@@ skipping 84 matching lines @@
   for (WmWindow* root : WmShell::Get()->GetAllRootWindows()) {
     observed_container_windows_.Add(
         root->GetChildByShellWindowId(kShellWindowId_DefaultContainer));
   }
 
   display::Screen::GetScreen()->AddObserver(this);
 }
 
 ShelfWindowWatcher::~ShelfWindowWatcher() {
   display::Screen::GetScreen()->RemoveObserver(this);
-  WmShell::Get()->RemoveActivationObserver(this);
+  if (WmShell::HasInstance())

[James Cook, 2016/08/17 03:29:39]

Why is this needed? ShelfWindowWatcher is owned by WmShell and reset in
WmShell::Shutdown(), so I would expect there to always be a WmShell instance
around.

[msw, 2016/08/17 17:45:44]

Fixed instead by calling WmShell::Shutdown in WindowManager; thanks!
(seems like we should have been doing that all along)

+    WmShell::Get()->RemoveActivationObserver(this);
 }
 
 void ShelfWindowWatcher::AddShelfItem(WmWindow* window) {
   const ShelfItemDetails* item_details = window->GetShelfItemDetails();
   ShelfItem item;
   ShelfID id = model_->next_id();
   item.status = window->IsActive() ? STATUS_ACTIVE : STATUS_RUNNING;
   SetShelfItemDetailsForShelfItem(&item, *item_details);
   window->SetIntProperty(WmWindowProperty::SHELF_ID, id);
   std::unique_ptr<ShelfItemDelegate> item_delegate(
@@ skipping 96 matching lines @@
     observed_container_windows_.Add(container);
 }
 
 void ShelfWindowWatcher::OnDisplayRemoved(const display::Display& old_display) {
 }
 
 void ShelfWindowWatcher::OnDisplayMetricsChanged(const display::Display&,
                                                  uint32_t) {}
 
 }  // namespace ash