WebVTT: Support 'auto' text position

This changes the behavior of the VTTCue.position attribute to match the
current spec. draft. It also changes the default of the same value when
parsed from a VTT file or created via the VTTCue constructor.

A number of tests where updated to reflect the new behavior (50 -> 'auto').

BUG=448000

Review URL: https://codereview.chromium.org/851933003

git-svn-id: svn://svn.chromium.org/blink/trunk@188753 bbb929c8-8fbe-4397-9dbb-9b2b20218538
21 files changed
tree: e178f790e271f9afbf9c7ccc9ecd2e9a9d75ab2a
  1. third_party/