Document calls to the "rules for updating the text track rendering"
Per spec there are only two calls to these rules:
* The last step of the "time marches on" algorithm.
* "When the user agent starts exposing a user interface for a video
element."
We have the first call, and two others that are needed when the text
track mode changes between hidden and visible. A spec bug was filed
for this case: https://www.w3.org/Bugs/Public/show_bug.cgi?id=28236
BUG=322434
NOTRY=true
Review URL: https://codereview.chromium.org/1022743002
git-svn-id: svn://svn.chromium.org/blink/trunk@192148 bbb929c8-8fbe-4397-9dbb-9b2b20218538
3 files changed
