VT: Dropping P-frames till I-frame provided am: 6ffdc403c8 am: 15cd5437f1

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/1591121

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I50783292fb32285d1f98957f3fbe18c0ccfb820e