GitLab

Makes GetFieldTrialParamValueByFeature() not do an extra field
trial look up by making it match the GetFieldTrialParamValue()
code path.

Also merges GetFieldTrialParamsWithoutFallback()'s contains and
map access into a single lookup, rather than two.

Bug: 1163921
Change-Id: I602e0ee47f679b143ee1666923b53a2760cae6c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2617470
Auto-Submit: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842188}