Update CompletionSuggestion bucket selection


Update CompletionSuggestion bucket selection

The data collected by this experiment doesn't make sense. On review
it was suggested to make a few changes:

  • don't use Math.random(), instead sample from the random pageId var.
  • unrelated to unrelable data collection, but removed logId as not necessary.
  • Ensure pageId is only generated once, and not multiple times, when participateInTest is called multiple times on a slow connection.
  • no longer blocks initial suggestions waiting for mw.loader.using

Bug: T112585
Change-Id: I0cb6fe37e88cf6810409d9dfe8da329ec1cd68f9
(cherry picked from commit dda2eae04c5bcd6759f98bebaa07c88fc965a504)