Breaking dependencies on XRDevice

Remove as many references to XRDevice as possible without completely
removing the interface itself. All functionality previously contained
in XRDevice is shifted into the XR interface. Done purely as a method of
reducing the size of the XRDevice removal CL.

Bug: 916299
TBR: mcasas
Change-Id: I01696972a7e56e196eedfc6ffe248789520a8f9e
Reviewed-on: https://chromium-review.googlesource.com/c/1405880
Commit-Queue: Brandon Jones <bajones@chromium.org>
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622128}
17 files changed