Revert "Remove old position adjustment for non-snap-to-lines WebVTT cues"

This reverts commit e6b16d301f0da8a22bfba7ab5997771af0459cf5.

Reason for revert: https://crbug.com/824746

Original change's description:
> Remove old position adjustment for non-snap-to-lines WebVTT cues
> 
> This is a remnant of what the spec originally said. Just like the bug
> report says, this turned out to be pretty confusing:
> https://www.w3.org/Bugs/Public/show_bug.cgi?id=19178
> 
> Bug: 551245
> Change-Id: I1063b940db81555a65211fa93e84441b53e2b091
> Reviewed-on: https://chromium-review.googlesource.com/753102
> Reviewed-by: Fredrik Söderquist <fs@opera.com>
> Commit-Queue: srirama chandra sekhar <srirama.m@samsung.com>
> Cr-Commit-Position: refs/heads/master@{#513819}

TBR=fs@opera.com,srirama.m@samsung.com

# Not skipping CQ checks because the original CL landed 4 months ago.

Bug: 551245
Change-Id: Ic0fa56ae68b11332f6e0336c290290f434c7df3c
Reviewed-on: https://chromium-review.googlesource.com/1004974
Commit-Queue: srirama chandra sekhar <srirama.m@samsung.com>
Reviewed-by: srirama chandra sekhar <srirama.m@samsung.com>
Cr-Commit-Position: refs/heads/master@{#549503}
2 files changed