Expose method for changing video background color

[victorkifer]

When you set video style to fit (setStyle(BaseVideoRenderer.STYLE_VIDEO_SCALE, BaseVideoRenderer.STYLE_VIDEO_FIT)) on PublisherKit or SubscriberKit, the video will be fit into the view and so it's possible to have black borders on some sides.

I would like to be able to change that color. IMO it makes sense to expose it via PublisherKit/SubscriberKit or BaseVideoRenderer. It seems like just storing it in renderer and using it in GLES20.glClearColor(); method should do the trick.

[v-kpheng]

Thanks, @victorkifer, for this suggestion.

There's no plans for this API but that may change in the future.

CC'ing @Daniel085, since this is product request.