Replace std::find_if in AdvanceUntil with a manual loop, which can
then return early, skipping the branch comparing to buffer_end_.

Change-Id: If49ed3667877751fcb0103a742750f03e5bd50db
Reviewed-on: https://chromium-review.googlesource.com/c/1411351Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58846}