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* Add support in AXPlatformNodeAuraLinux::AddAccessibilityTreeProperties
  and use in  AccessibilityTreeFormatterAuraLinux::ProcessTreeForOutput.
* By default, output all relation types but embedded-by (which appears
  on all top-level documents).
* Update auralinux expectations where relations are implemented.

Bug: 946016
Change-Id: I8792ddf23f23ad74b1b378f9cfb01f906b967590
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1540283
Commit-Queue: Martin Robinson <mrobinson@igalia.com>
Auto-Submit: Joanmarie Diggs <joanmarie.diggs@gmail.com>
Reviewed-by: Martin Robinson <mrobinson@igalia.com>
Cr-Commit-Position: refs/heads/master@{#644607}