Fix video positioning in full view mode.

**Issue**: Transcript cutting off view of video especially in full view mode.

**Fix**: Improved javascript logic for resizing + transcripts already haven't layered on top of video.

**Ticket**: [BLD-852](https://edx-wiki.atlassian.net/browse/BLD-852)

@jmclaus @valera-rozuvan @olmar please review.