mash: Relay some Chrome aura window properties to Ash.

ui/views/mus/desktop_window_tree_host_mus.cc

Index: ui/views/mus/desktop_window_tree_host_mus.cc
diff --git a/ui/views/mus/desktop_window_tree_host_mus.cc b/ui/views/mus/desktop_window_tree_host_mus.cc
index 12d11166f2452f579f464c2aa520cc1357488595..cc5b932147d466c36202487a11b9c503157b8b7d 100644
--- a/ui/views/mus/desktop_window_tree_host_mus.cc
+++ b/ui/views/mus/desktop_window_tree_host_mus.cc
@@ -182,6 +182,7 @@ DesktopWindowTreeHostMus::DesktopWindowTreeHostMus(
   aura::Env::GetInstance()->AddObserver(this);
   MusClient::Get()->AddObserver(this);
   native_widget_delegate_->AsWidget()->AddObserver(this);
+  desktop_native_widget_aura->content_window()->AddObserver(this);

[sky, 2017/01/27 16:20:20]

You never remove this observer.

[msw, 2017/01/27 19:11:34]

Now done in the destructor.

   // DesktopNativeWidgetAura registers the association between |content_window_|
   // and Widget, but code may also want to go from the root (window()) to the
   // Widget. This call enables that.
@@ -679,6 +680,11 @@ void DesktopWindowTreeHostMus::OnWindowManagerFrameValuesChanged() {
   SendHitTestMaskToServer();
 }
 
+void DesktopWindowTreeHostMus::OnWindowPropertyChanged(aura::Window* window,
+                                                       const void* key) {
+  // Ignore this; window property changes are handled elsewhere.
+}
+
 void DesktopWindowTreeHostMus::OnWidgetActivationChanged(Widget* widget,
                                                          bool active) {
   // TODO(erg): Theoretically, this shouldn't be necessary. We should be able
@@ -688,6 +694,12 @@ void DesktopWindowTreeHostMus::OnWidgetActivationChanged(Widget* widget,
   is_active_ = active;
 }
 
+void DesktopWindowTreeHostMus::OnWindowPropertyChanged(aura::Window* window,
+                                                       const void* key,
+                                                       intptr_t old) {
+  MusClient::Get()->OnWindowPropertyChanged(window, key);

[sky, 2017/01/27 16:20:20]

I recommend something like this:

MusClient::Get()->MirrorPropertyFromWidgetWindowToRootWindow(window, key,
window());

Hopefully that better conveys what is expected to happen when this occurs. Does
it make it any clearer to you?

I suggested lumping this on MusClientObserver, but I think it would be clearer
to have an explicit interface for this function, perhaps MusPropertyMirror.
WDYT?

[msw, 2017/01/27 19:11:34]

I tried to adopt your suggestions, let me know what you think.

+}
+
 void DesktopWindowTreeHostMus::ShowImpl() {
   native_widget_delegate_->OnNativeWidgetVisibilityChanging(true);
   // Using ui::SHOW_STATE_NORMAL matches that of DesktopWindowTreeHostX11.