Exempt status bubble windows from status bar darkening

ash/wm/window_properties.h

Index: ash/wm/window_properties.h
diff --git a/ash/wm/window_properties.h b/ash/wm/window_properties.h
index f70487a52ad9bedadaaa17e84c710a504d2d0b3b..446671e36815ae928a8d3b568a5f2eb5d9f9c703 100644
--- a/ash/wm/window_properties.h
+++ b/ash/wm/window_properties.h
@@ -33,6 +33,11 @@ extern const aura::WindowProperty<internal::AlwaysOnTopController*>* const
 extern const aura::WindowProperty<bool>* const
     kChildWindowVisibilityChangesAnimatedKey;
 
+// True if the window is ignored by the shelf layout manager for purposes of
+// darkening the shelf.
+extern const aura::WindowProperty<bool>* const
+    kIgnoredByShelfKey;
+
 // Used to remember the show state before the window was minimized.
 extern const aura::WindowProperty<ui::WindowShowState>* const
     kRestoreShowStateKey;