[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}
bool ShouldUseNativeViews() {

bool ShouldUseNativeViews() {
#if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX)
  return base::FeatureList::IsEnabled(kAutofillExpandedPopupViews) ||
         base::FeatureList::IsEnabled(::features::kExperimentalUi);
#else
  return false;
#endif
}
