Align reference box computation for inline boxes with Gecko

For inline boxes, the reference box should be computed per-fragment, and
be subject to box-decoration-break. We're not quite there yet though, so
go for "local compat" for now and align with Gecko. This way we're
slightly closer to "correct" (the "single line" case ought to be fairly
correct for instance), and hopefully avoid getting sucked into a compat
"sinkhole".
Adjust css3/masking/clip-path-reference-box-inline.html to match.

BUG=641907
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2303773002
Cr-Commit-Position: refs/heads/master@{#416264}
3 files changed