GitLab

This is a reland of 86c3def7

Changed this to use a field on BuildConfig.java so it wouldn't change
the native lib.

Original change's description:
> Add synthetic field trial for isolated splits
>
> This should make analysis easier for a binary experiment, since the
> Finch dashboard can be used.
>
> Bug: 1150162
> Change-Id: Id90204398234938c441982d5c2bc5c6f7c63d575
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2545874
> Commit-Queue: Clark DuVall <cduvall@chromium.org>
> Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#829494}

Bug: 1150162
Change-Id: I9447c7f5e1303f036545287738028443c67551d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2554032Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#830242}