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 - specifying types of constants.
 - clarifying comment references to functions and variables.
 - adding `using` aliases to shorten long library type names.
 - adding explicit type for value returned from library.

These changes came out of suggestions from thestig@ on crrev.com/c/1949807

R=thestig, akihiroota, dmazzoni

Change-Id: I25fc99843c27f7a41403f15e3e82d688fd5b44fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2096417
Commit-Queue: Chris Hall <chrishall@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Akihiro Ota <akihiroota@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749064}