Remove ScriptScope

It's no longer used.

BUG=357144
NOTRY=true

Review URL: https://codereview.chromium.org/255783004

git-svn-id: svn://svn.chromium.org/blink/trunk@172694 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove always-false settings for text track selection

Since these settings were not exposed to Chromium or set in any other
way, they were always false. shouldDisplayTextDescriptions was not even
used internally.

While the text track selection needs to be improved, but these settings
made it look like it was more sophisticated than it really is. A new
setting for hard-of-hearing users (preferring captions over subtitles)
may eventually be needed, but that would be a single setting only.

The removed comment no longer makes sense, because the maximum value
returned by textTrackSelectionScore is now the return value of
textTrackLanguageSelectionScore, which is not greater than itself...

BUG=none

Review URL: https://codereview.chromium.org/250923003

git-svn-id: svn://svn.chromium.org/blink/trunk@172695 bbb929c8-8fbe-4397-9dbb-9b2b20218538