Pending Timeline Region Readability
Pending Timeline Region Readability

When trying to understand how the timeline regions were working
in player, I found it a little too spread-out and missing notes.

I have moved some parts closer to where they are used and added some
comments explaining why the code exists.

Change-Id: If4c52e245220f3703a411f70298db2c49dc73255

shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,tvoli/shaka-player,tvoli/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player