desktop-pwas: Introduce experimental link capturing flag

Currently, link capturing is enabled by the EnableDesktopPWAWindowing
feature, but in the future, it will be disabled unless you also have
this flag turned on.

Bug: 814102
Change-Id: Ia13f48d38d963d8a2b93b327cb9866213390cd19
Reviewed-on: https://chromium-review.googlesource.com/936524
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539707}
6 files changed