am 930189f0: am df71cabb: cherrypick Change-Id: Ica1b68a1687917432d39d7d116c9c24fa1644a83 Initial posting of in-app billing docs

* commit '930189f0f7c302dc76031d88f7a90f32bb57e7b6':
  cherrypick Change-Id: Ica1b68a1687917432d39d7d116c9c24fa1644a83 Initial posting of in-app billing docs