Provides a class that initiates AB-test bucketing and registers
as a MF module. Activates the reading depth test for users who are bucketed
in either buckets "A" or "B".
Does not add event-logging or visual style changes for page issues AB test.
Bug: T193584
Change-Id: If8504a35059c6d1b056cef063a595b1c2ffd351a
