This extension is used to query strings from an array based on index,
which will be used to query all the information about workarounds in
ANGLE.

Bug: angleproject:1621

Change-Id: I27157f278f7f17c92c8b4fd7753e2a5ecd0528f6
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1627723
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>