Tells you how many things you've allocated.
Will be used for various optimizations.
Change-Id: I8a31bb06e2b23781245bbfd16fabc9b85e440d14
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96142
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>