A tree of query to data. Has utilities for reducing the tree based on a
custom merger function.
Bug: dawn:1342
Change-Id: If1c0503be05ee04bcf55dd5bdc9aa3caf6fb56ee
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/87222
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>