Reduce code duplication in checked iterators.

Bug: 817982
Change-Id: Ie915fe65fe1804e5c955ed5fa09ba3e7b6a93330
Reviewed-on: https://chromium-review.googlesource.com/c/1369031
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Chris Palmer <palmer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614917}
1 file changed