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

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I326fc7a3731c45cde898aeb641cdf065c58ff5db