Add parsing support for display: contents, and minimum behavior similar to display: none
The following commit adds parsing for the display: contents value, gated after a
runtime enabled feature, and adds the basic code for display: contents elements
to not generate a LayoutObject.
BUG=
657748
TEST=LayoutTests/css-display-3/display-contents-set-get.html
Committed:
https://crrev.com/310aa236042e11fc39958ab02e9ff55b393fced8
Cr-Commit-Position: refs/heads/master@{#427437}