Adding an experiment to automatically open the default browser chooser

TBR=pmonette@chromium.org

Bug: 751299
Change-Id: I3d2026ad1b48652ba38cfcb73c073c58878bf956
Reviewed-on: https://chromium-review.googlesource.com/949974
Reviewed-by: Patrick Monette <pmonette@chromium.org>
Cr-Commit-Position: refs/branch-heads/3325@{#663}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
7 files changed