Merge branch 'stable-2.9'

* stable-2.9:
  Fix indentation in RelatedChanges.java
  Show Related Changes for merged changes if there are open descendants
  Review UI docs: List missing unified diff view as limitation of new UI
  Index colors of screenshots in review UI documentation

Change-Id: I7b799cb8200927a2a256218bd232e5bb7b4c584d