Merge "Add some warnings and notes about framework's jarjar rules" into sc-dev...

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

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

Change-Id: If5b924150edfff601c1f113e43abe80b38dc0774