Test coverage for bug in WmWindowAura::OnWindowVisibilityChanged()

ash/mus/bridge/wm_window_mus.cc

Index: ash/mus/bridge/wm_window_mus.cc
diff --git a/ash/mus/bridge/wm_window_mus.cc b/ash/mus/bridge/wm_window_mus.cc
index d0234c695586fd97b05db357c1b954d07c1212b0..ae121ab05cd5abfe5bdc46ef38c3d3ca1b26638f 100644
--- a/ash/mus/bridge/wm_window_mus.cc
+++ b/ash/mus/bridge/wm_window_mus.cc
@@ -922,6 +922,17 @@ void WmWindowMus::OnWindowDestroyed(ui::Window* window) {
   FOR_EACH_OBSERVER(WmWindowObserver, observers_, OnWindowDestroyed(this));
 }
 
+void WmWindowMus::OnWindowVisibilityChanging(ui::Window* window) {
+  DCHECK_EQ(window_, window);
+  FOR_EACH_OBSERVER(WmWindowObserver, observers_,
+                    OnWindowVisibilityChanging(this, !window->visible()));
+}
+
+void WmWindowMus::OnWindowVisibilityChanged(ui::Window* window) {
+  FOR_EACH_OBSERVER(WmWindowObserver, observers_,
+                    OnWindowVisibilityChanged(Get(window), window->visible()));

[James Cook, 2016/09/28 01:19:58]

Why doesn't it use |this|?

[sky, 2016/09/28 18:16:36]

You would think so, eh? aura::WindowObserver:OnWindowVisibiltyChanged (and
ui::WindowObserver::onWindowVisibilityChanged()) is called on observers attached
to all descendants and ancestors. The |window| parameter to
OnWindowVisibilityChanged() is the window Show/Hide was called on, not
necessarily the one the observer was added to. Confusing, eh?

[James Cook, 2016/09/28 19:02:49]

Wow, it's super confusing that Changing() and Changed() have different
semantics. I guess we're stuck with that behavior and those names from aura.
Yuck.

+}
+
 void WmWindowMus::OnTransientChildAdded(ui::Window* window,
                                         ui::Window* transient) {
   FOR_EACH_OBSERVER(WmTransientWindowObserver, transient_observers_,