[Autofill] Remove AutofillPopupViewViews and associated feature.

Bug: 906135,831603
Change-Id: I3c982f8b3ffb4928c7c878e74e10113999106499
Reviewed-on: https://chromium-review.googlesource.com/c/1387124
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Reviewed-by: Fabio Tirelo <ftirelo@chromium.org>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Commit-Queue: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621360}
  FlagsStateSingleton()
      : flags_state_(kFeatureEntries, base::size(kFeatureEntries)) {}

  FlagsStateSingleton()
      : flags_state_(kFeatureEntries, base::size(kFeatureEntries)) {}
