Allow the default mode for video peek to be undefined

Forcing the default mode for video peek to be defined to on has broken
use cases for Broadcom devices. See topic for related CLs that allow
for legacy undefined modes when video peek has not been specified by the
app.

See go/video-peek-legacy-mode for more details.

Bug: 220266078
Test: atest android.media.decoder.cts.DecoderTest#testTunneledVideoPeekOnVp9
Change-Id: I3612524f0bf5a9ac46e2b55342f5e6dacefa5094
1 file changed