Merge "Expose TEST_TAP_PREFIX as system API" am: f614cdce9d am: bb6c348b0f am: 35447ff76a

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1579503

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ia3a9078ce1e823c4762e193cbc27b7ab7d8932a8