mash: Create and show a shelf in mash.

ui/views/mus/pointer_watcher_event_router.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 "ui/views/mus/pointer_watcher_event_router.h"
 
 #include "services/ui/public/cpp/window.h"
 #include "services/ui/public/cpp/window_tree_client.h"
 #include "ui/events/base_event_utils.h"
 #include "ui/events/event.h"
@@ skipping 26 matching lines @@
 
   bool had_watcher = HasPointerWatcher();
   pointer_watchers_.AddObserver(watcher);
   if (!had_watcher) {
     // First PointerWatcher added, start the watcher on the window server.
     window_tree_client_->StartPointerWatcher(want_moves);
   }
 }
 
 void PointerWatcherEventRouter::RemovePointerWatcher(PointerWatcher* watcher) {
+  DCHECK(pointer_watchers_.HasObserver(watcher));

[James Cook, 2016/08/17 18:31:50]

FYI - We'll have to see how this goes. I vaguely remember seeing some code that
could attempt to remove the same PointerWatcher twice. That said, removing twice
seems like a dumb thing to do, so I support the DCHECK.

[msw, 2016/08/17 18:55:17]

Acknowledged.

   pointer_watchers_.RemoveObserver(watcher);
   if (!HasPointerWatcher()) {
     // Last PointerWatcher removed, stop the watcher on the window server.
     window_tree_client_->StopPointerWatcher();
     pointer_watcher_want_moves_ = false;
   }
 }
 
 void PointerWatcherEventRouter::OnPointerEventObserved(
     const ui::PointerEvent& event,
@@ skipping 23 matching lines @@
   base::ObserverList<PointerWatcher>::Iterator iterator(&pointer_watchers_);
   return !!iterator.GetNext();
 }
 
 void PointerWatcherEventRouter::OnWindowTreeCaptureChanged(
     ui::Window* gained_capture,
     ui::Window* lost_capture) {
   FOR_EACH_OBSERVER(PointerWatcher, pointer_watchers_, OnMouseCaptureChanged());
 }
 
-void PointerWatcherEventRouter::OnWillDestroyClient(
+void PointerWatcherEventRouter::OnDidDestroyClient(
     ui::WindowTreeClient* client) {
+  DCHECK(!pointer_watchers_.might_have_observers());

[sky, 2016/08/17 19:50:36]

I suspect we'll have to remove this, but we can try it. My concern is that
PointerWatcherEventRouter::OnDidDestroyClient may be called before other places
do their cleanup.

   DCHECK_EQ(client, window_tree_client_);
   window_tree_client_->RemoveObserver(this);
   window_tree_client_ = nullptr;
 }
 
 }  // namespace views