The TODO was about wrapping together the sourceposition iterator and the bytecode
iterator. Since the first one is useful in fewer parts than the second, and the
bytecode iterator is more flexible to advance than the sourceposition iterator,
and we would not gain that much more readability, this TODO is removed.

TBR=mstarzinger@chromium.org

Bug: 
Change-Id: I104d0f5f0cd01686ea48d209419bd6bb2ed19bcf
Reviewed-on: https://chromium-review.googlesource.com/621106
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47432}