Revert of Catch up the spec update in CSS Rhythmic Sizing (patchset #7 id:120001 of https://codereview.chromium.org/2704343003/ )

Reason for revert:
Broke https://build.chromium.org/p/chromium/builders/Linux%20x64

See https://build.chromium.org/p/chromium/builders/Linux%20x64/builds/34559 and https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium%2FLinux_x64%2F34559%2F%2B%2Frecipes%2Fsteps%2Fcompile_confirm_no-op%2F0%2Fstdout

Original issue's description:
> Catch up the spec update in CSS Rhythmic Sizing
>
> This patch catches up spec changes in CSS Rhythmic Sizing[1]. In
> particular:
> 1. The property name was changed to 'line-height-step'.
> 2. The value syntax was changed to single <length>.
> 3. The baseline position feature was removed.
>
> Tests in csswg-test were updated[2] and imported to fail. All of them
> pass in this patch.
>
> The feature is still behind the flag.
>
> [1] https://drafts.csswg.org/css-rhythm/
> [2] https://github.com/w3c/csswg-test/commit/50a861a451a1fe9cc80044568c257212729779fa
>
> BUG=586413
>
> Review-Url: https://codereview.chromium.org/2704343003
> Cr-Commit-Position: refs/heads/master@{#455008}
> Committed: https://chromium.googlesource.com/chromium/src/+/2344921f94b85be9884ed847d9a041a5e2575946

TBR=meade@chromium.org,sashab@chromium.org,eae@chromium.org,kojii@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=586413

Review-Url: https://codereview.chromium.org/2737673003
Cr-Commit-Position: refs/heads/master@{#455020}
21 files changed