Not including <iterator> creates problems on some build systems because
std::back_inserter is defined there.
Bug: None
Change-Id: I27180f72dd327e3a0caab35d3a33907f1e0c4296
Reviewed-on: https://webrtc-review.googlesource.com/69323
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22825}