Include display:contents elements in accessibility tree

Bug: 835455
Change-Id: If3f4eacb975a8ee50a66bb787a55d257633cfb1e
Reviewed-on: https://chromium-review.googlesource.com/c/1242572
Commit-Queue: Alice Boxhall <aboxhall@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609515}
8 files changed