This allows us to remove the PatternRewriter.

Change-Id: I54ec74ed3bd31e76e38c69f9b0b2a78f8620cd89
Reviewed-on: https://chromium-review.googlesource.com/c/1429863
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59028}