GitLab

This makes canvas.getContext("gpupresent") return a GPUCanvasContext
when the --enable-unsafe-webgpu flag is present.

BUG=chromium:877147

Change-Id: I74b35cf117aadcc00a979189b8364798b353ac66
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1559181Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#650595}