This is incorrect in the specific case of aria-labelledby, it's allowed to point to hidden nodes and we already have quite a few tests for this.

The change is probably correct for aria-flowto and aria-controls.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e0989c034eec8d6fcbb55f03a004fec2a32e83d7

commit e0989c034eec8d6fcbb55f03a004fec2a32e83d7
Author: nektar <nektar@chromium.org>
Date: Mon Jul 11 18:35:03 2016

Ignores ARIA relations (e.g. aria-labelledby) that point to an invisible target.

BUG= 625356 
R=dmazzoni@chromium.org, aboxhall@chromium.org
TESTED=layout tests, manually with Jaws

Review-Url: https://codereview.chromium.org/2112243004
Cr-Commit-Position: refs/heads/master@{#404696}

[add] https://crrev.com/e0989c034eec8d6fcbb55f03a004fec2a32e83d7/third_party/WebKit/LayoutTests/accessibility/aria-relations-should-ignore-hidden-targets.html
[modify] https://crrev.com/e0989c034eec8d6fcbb55f03a004fec2a32e83d7/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp

Fixed according to comment 2.