Add a control group to the SiteIsolationExtensionsActive.
"Control" corresponds to the Disabled group of the [non-synthetic]
SiteIsolationExtensions field trial. In practice, our analysis
has been skewed by the fact that SiteIsolationExtensionsActive/Default
includes samples from populations where the SiteIsolationExtensions trial was
not operative; these samples were a source of confounding variables.
BUG=542921
Review URL: https://codereview.chromium.org/1682253006
Cr-Commit-Position: refs/heads/master@{#375027}
2 files changed
