Two values were retrieved from quad neighbors; layer and ma.  The value
of ma was retrieved as the helper invocations would otherwise have a
different value as the major axis.

This change makes the helpers rechoose ma based on the layer, which
removes a number of subgroup operations.  This is also more precise as
the major axis value could be slightly different from the neighbor.

Bug: angleproject:3732
Change-Id: I3c8ca724e91c52ca2f7edc03bb0e5dca67610ff4
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1742215Reviewed-by: Tobin Ehlis <tobine@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>