The Flatpanelshd.com blog site has been tracking HDR support from Google Play and now counts 42 movies as being available in UltaHD and HDR including e ‘Mad Max: Fury Road’, ‘Batman vs. Superman’, ‘Fantastic Beasts and Where to Find Them’, and ‘Kong: Skull Island’. The titles are available on the service at prices from $20 to $30. The 42 are a subset of the more than 125 titles available in UltraHD.
You can find a full list of titles here.