Preview while seeking in a paused state.

Created by: wilaw

Today if you pause the player and then seek, the image that is rendered remains the image that was playing when paused. This gives an unnatural behavior to the rendering surface. A preferred implementation is that the static image reflects the new position of the scrubhead in the video.

The image should only change when the seek is complete (and the scrub handle dropped) and not while scrubbing. This is not a request for fast-forward scrub.

Under the covers, the player should build up at least it's starting buffer, so that when play() is called again playback is instant.