Merge "Add some warnings and notes about framework's jarjar rules" into sc-dev am: c8863205 am: 84af0b45 am: 7ef9cb7f

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/14703099

Change-Id: Ie5a34ce22f59c2d0de170e6fd371ba27dadc6794