Merge change 2716 into donut

* changes:
  Update MediaPlayer to allow setVideoSurface calls after prepare. Also allow passing a null surface. The API is now enabled to change the surface while the video is playing. This could allow orientation changes during playback or to allow the audio track from a video to play in the background. NOTE: There are still changes required to pmem driver to allow remapping shared physical memory into a process in order for this to work. This change only enables the API to send the appropriate calls when the lower level code supports it.