This is necessary for prewarming. With prewarming, in a sequence of 2
videos, the second renderer is enabled before the first one is disabled,
and decode-only frames should be skipped before the second renderer is
started. The problem is that the second renderer will forward frames to
a BufferingVideoSink before it is started, which will delay the frame
handling and therefore not skip the frame before the renderer is
started.
PiperOrigin-RevId: 721032049
9af43c7381