This patch remove render pipeline builder and use descriptor to create render pipeline.
Sub-objects in descriptor will be removed in future.
Bug: dawn:4
Change-Id: I58dd569c7be42c2648311847b939c681189c2854
Reviewed-on: https://dawn-review.googlesource.com/c/2180
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>