Import AndroidX from build 6848393

  ./update_prebuilts.py -x 6848393

  Import AndroidX heifwriter only from build 6848393 in order to
  pick up a fix for b/168660257.

This is the same update as Ibfe07237c4a0dca937dacf186c6618d7fb439fb1
on git-master, but pulled from androidx-master-dev (instead of androidx-
platform-dev) for mainline-prod.

Change-Id: Ibfe07237c4a0dca937dacf186c6618d7fb439fb1
Merged-In: Ibfe07237c4a0dca937dacf186c6618d7fb439fb1
15 files changed