This also changes VulkanInfo to gather info on backends / adapters
instead of the device, because all the info gathering can happen before
the device is created.
BUG=dawn:29
Change-Id: I9dc4412f494428f1ae589544d3adf76fe8b9a3a3
Reviewed-on: https://dawn-review.googlesource.com/c/3941
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>