Allow the default mode for video peek to be undefined am: 19203eb6 am: 4b0e365b

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/18310317



Change-Id: I449f6c8471e01e23d8bda2d8a9230b8f5525e157
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>