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This adds one more AR sample page that relies on incubated plane
detection API to implement synchronous hit test purely in JavaScript.

Change-Id: I7d98fb5f656eb4068facf83b4de8ac9a7b49f334
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1597276Reviewed-by: Brandon Jones <bajones@chromium.org>
Commit-Queue: Piotr Bialecki <bialpio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658283}