Bring reference space naming/interfaces up to spec

eye-level -> local
floor-level -> local-floor
bounded -> bounded-floor
identity -> viewer

XRSession.viewerSpace is removed.

Bug: 963155, 961906, 953488
Change-Id: I5ab8b23ec14ffd5e2b272238b7fa11a29b11f09b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1616525
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Commit-Queue: Bill Orr <billorr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662072}
68 files changed