If DiscussionToolsABTest is enabled (set to `all` or a feature), logged
in users who have never used the tool before will be assigned to an a/b
test bucket. If they're in the test bucket, they get the feature
enabled.
If they manually set their beta feature preference, we don't override
that but do maintain their bucket for logging purposes.
Bug: T268191
Change-Id: I9c4d60e9f9aaef11afa7f8661b9c49130dde3ffa
Also, stop the dialog-prevent-show event from switching editor_interface
just because it's tied to the `editor-switch` feature.
Bug: T259673
Change-Id: I2acf9d79add281ed0f62f022e44bb18948ceafc8
