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There are several problems with current openxr implementation:
1. stage bounds is fixed and only need to be set once.
2. Some VRDisplayinfo variables don't need to wait for session start
to be populated on every frame.

Change-Id: I9c0e6b8aea3560f5694a0b818f827cd2c0f30e01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832484
Commit-Queue: Zheng Qin <zheqi@microsoft.com>
Reviewed-by: Alexander Cooper <alcooper@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710176}