am 20b213c7: am 64fc8082: am 40057ce7: Document that stopPreview is not needed before takePicture.

Merge commit '20b213c7dd9d18d092a60ea176dd83cc29d6be80'

* commit '20b213c7dd9d18d092a60ea176dd83cc29d6be80':
  Document that stopPreview is not needed before takePicture.