Use border-box as the reference box for (-webkit-)clip-path
The 'clip-path' property should use the border box as the reference box
(per default; <geometry-box> not yet supported) [1].
The new behavior matches WebKit and Gecko (except for inline boxes,
see below.)
For inline boxes that span multiple lines we use the union of all the
lines. The test css3/masking/clip-path-reference-box-inline.html added
to track this behavior.
[1]
https://drafts.fxtf.org/css-masking-1/#the-clip-path
BUG=
418484
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Committed:
https://crrev.com/70b5b81d191f2cf8057f5609ed1e53ee392f7ea1
Cr-Commit-Position: refs/heads/master@{#414118}