Improve readability for ContextualSearchFieldTrial

Improvement after https://chromium-review.googlesource.com/c/chromium/src/+/1565311 - making file a little bit shorter and more readable (different sorting entries, using switch, etc.)

Change-Id: I64f71a8b15e211a11706ccb376b0474839a5ec92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1579720
Reviewed-by: Donn Denman <donnd@chromium.org>
Commit-Queue: Marcin Wiącek <marcin@mwiacek.com>
Cr-Commit-Position: refs/heads/master@{#653753}
1 file changed