Device child objects were storing an *unstable* pointer to device
specific tracking information. Fix this by moving the tracking
information to a stable heap allocation.
Bug: dawn:565
Change-Id: I00ad72563ac66e29314603e77698718953fcbf15
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/38280
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>