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Creates and implements the missing delegates for enterprise reporting
on iOS.

Note that this won't be functional yet because of an issue with the
way ApplicationContext instantiates its shared URLLoaderFactory. That
issue will be fixed in a separate CL.

#Squeegee

Bug: 1066495
Change-Id: Idb493efeca63bb19eaf250ede02608f6bd842a81
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2341995
Commit-Queue: Guillaume Jenkins <gujen@google.com>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797290}