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Use more C++11. Along the way, also use base::Contains() in more places
and improve STL usage.

Change-Id: I34e96d3d9801bcdf30f0f10eea2f5ca91ed43508
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863157Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706284}