fix: Add missing require in region_timeline.js
fix: Add missing require in region_timeline.js

Change-Id: I9dc9a6dbe5be443963e86ea4fd578dadb47b296d

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