am 2fcba612: am 618ded26: am a6602f1f: Add docs for SDK update. Add redirects for preview files. Manually integrate a few doc changes from cupcake.

Merge commit '2fcba6125ff9f3b8d8d555e20775f4bed0462029'

* commit '2fcba6125ff9f3b8d8d555e20775f4bed0462029':
  Add docs for SDK update.