VTTCue: Support 'auto' for line

Since the setter is no longer limitting the value to [0, 100] we need to
store an additional flag for the 'auto' value.
Minor updates to VTTCue::calculateComputedLinePosition to match updated
spec. (this is now where the line value is checked against the above
range.)

BUG=448000

Review URL: https://codereview.chromium.org/850363005

git-svn-id: svn://svn.chromium.org/blink/trunk@188723 bbb929c8-8fbe-4397-9dbb-9b2b20218538
18 files changed
tree: dd98fa14dc89d26038c0e1f5aa2d7809c4fb5c7b
  1. third_party/