Courtney noted this bug from a review. Should begin label on pushGroup
instead of insert label.

Bug: b/154030403
Change-Id: I5f4da5762e1ef03fe27b414740e34d2064af86b5
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2171951Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>