Merge to M51: Accessible name calc should allow aria-labelledby to reference aria-hidden

Merge to M51: Accessible name calc should allow aria-labelledby to reference aria-hidden

The new accessible name calculation improved compatibility overall but broke
one specific case, where one element uses aria-labelledby (or aria-describedby)
to reference a subtree that's explicitly aria-hidden. The correct thing to
do here is ignore aria-hidden when an element is referenced explicitly.

<input aria-labelledby="label">
<div id="label" aria-hidden="true">Hidden label</div>

BUG=595494
Review URL: https://codereview.chromium.org/1917943002

Cr-Commit-Position: refs/heads/master@{#389798}
(cherry picked from commit 8dacc7a16ffdee2d4af5a60f6f9079c22fd7399c)

Committed: https://chromium.googlesource.com/chromium/src/+/6569fe5bbb0fca1b01108549ccbe0916e1d231eb

[dmazzoni, 2016-04-28 23:07:51]

Description was changed from

==========
Merge to M51: Accessible name calc should allow aria-labelledby to reference
aria-hidden

The new accessible name calculation improved compatibility overall but broke
one specific case, where one element uses aria-labelledby (or aria-describedby)
to reference a subtree that's explicitly aria-hidden. The correct thing to
do here is ignore aria-hidden when an element is referenced explicitly.

<input aria-labelledby="label">
<div id="label" aria-hidden="true">Hidden label</div>

BUG=595494

Review URL: https://codereview.chromium.org/1917943002

Cr-Commit-Position: refs/heads/master@{#389798}
(cherry picked from commit 8dacc7a16ffdee2d4af5a60f6f9079c22fd7399c)
==========

to

==========
Merge to M51: Accessible name calc should allow aria-labelledby to reference
aria-hidden

The new accessible name calculation improved compatibility overall but broke
one specific case, where one element uses aria-labelledby (or aria-describedby)
to reference a subtree that's explicitly aria-hidden. The correct thing to
do here is ignore aria-hidden when an element is referenced explicitly.

<input aria-labelledby="label">
<div id="label" aria-hidden="true">Hidden label</div>

BUG=595494

Review URL: https://codereview.chromium.org/1917943002

Cr-Commit-Position: refs/heads/master@{#389798}
(cherry picked from commit 8dacc7a16ffdee2d4af5a60f6f9079c22fd7399c)

Committed:
https://chromium.googlesource.com/chromium/src/+/6569fe5bbb0fca1b01108549ccbe...
==========

[dmazzoni, 2016-04-28 23:07:53]

Committed patchset #1 (id:1) manually as
6569fe5bbb0fca1b01108549ccbe0916e1d231eb.