Let WebVTTRegions depends_on=VideoTrack and simplify IDL

BUG=313604

Review URL: https://codereview.chromium.org/54903008

git-svn-id: svn://svn.chromium.org/blink/trunk@161218 bbb929c8-8fbe-4397-9dbb-9b2b20218538
3 files changed
tree: 05b3830a17744659d3f9a3d298da6319277add40
  1. third_party/