Converts ash/wm/mru_window_tracker_unittest.cc to use AshTest

ash/mus/property_util.h

Index: ash/mus/property_util.h
diff --git a/ash/mus/property_util.h b/ash/mus/property_util.h
index a0ede0188ae480c7d118266e94c1f36897b9dd73..1e9a0a89f035c5b483457ea200e4b4014ffaa395 100644
--- a/ash/mus/property_util.h
+++ b/ash/mus/property_util.h
@@ -88,6 +88,12 @@ bool ShouldRenderParentTitleArea(ui::Window* window);
 // kInvalidDisplayID.
 int64_t GetInitialDisplayId(const ui::Window::SharedProperties& properties);
 
+// Manipulates the kExcludeFromMru_Property property.
+void SetExcludeFromMru(ui::Window* window, bool value);
+
+// Returns true if the property is set and true, otherwise false.
+bool GetExcludeFromMru(const ui::Window* window);
+
 }  // namespace mus
 }  // namespace ash