TEST=conformance2/rendering/clear-func-buffer-type-match.html

BUG=angleproject:1954

Change-Id: Iefeb38041608f11781f87aadb8611737ba2ee96f
Reviewed-on: https://chromium-review.googlesource.com/461270
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>