Fix 'text-underline-position: under' to use em height ascent/descent
This patch changes underline position when 'text-underline-position:
under' is set to the "em height ascent/descent".
Due to large internal leadings in many modern East Asian fonts,
underlines are often drawn too far. This patch changes it to match to
Gecko.
The spec[1] defines to draw under the text content area, which CSS2
leaves explicitly undefined[2].
[1] https://drafts.csswg.org/css-text-decor-3/#underline-under
[2] https://drafts.csswg.org/css2/visudet.html#leading
BUG=681857
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Review-Url: https://codereview.chromium.org/2643413002
Cr-Commit-Position: refs/heads/master@{#468821}
26 files changed
