https://www.google.com/design/spec/patterns/navigation.html#navigation-patterns heading "Expanding navigation drawer"
Works, but after expanding the layer entry some of the other entries look weird.
Also there are "^" and "v" in the background. They shouldn't be visible for non-expandable groups
Should be fixed now
https://www.google.com/design/spec/patterns/navigation.html#navigation-patterns heading "Expanding navigation drawer"