WebXR: Fix anchor registration order, fix sample

Ensure that the anchors_data in a frame is populated after processing
anchors creation for that frame. This fixes an issue where a new anchor
was reported as created in the promise, but only started appearing in
the frame's list of anchors with a one-frame delay, resulting in losing
custom data that the application may have stored on the anchor
object.

Also update the example to fix a couple of misused fields for non-reticle
mode. This should fix the issue where the sunflowers weren't appearing
at the touched point.

Change-Id: I042f2e88f1fa4f0e09bacfcd4b93c89abe501bf6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1903822
Commit-Queue: Klaus Weidner <klausw@chromium.org>
Commit-Queue: Piotr Bialecki <bialpio@chromium.org>
Auto-Submit: Klaus Weidner <klausw@chromium.org>
Reviewed-by: Piotr Bialecki <bialpio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713711}
2 files changed