Fix for the flicker while changing the resolution in DashPlayer

- Just notify the message of MEDIA_SET_VIDEO_SIZE to JAVA Layer,
  while beginning to play the streaming.
- After the streaming begin to play, don't notify this message,
  while changing the resolution or seek operation finished.
- If we don't set video size,
  windowsmanager will adapt the dimension of the clip by itself.

Change-Id: I82c67f8e9011ed982cde5c0fc8f41e7151f76fc2
CRs-fixed: 451993
Signed-off-by: Hieu Phan <aznrice2k4@gmail.com>