Remove ScrollableArea::IsScrollable and IsProgrammaticallyScrollable.

The first is redundant with PLSA::ScrollsOverflow; the other is unused.

Also remove LFV::GetScrollingReasons, which was used in a confusing way
by MainThreadScrollingReasonsPerFrame.

Bug: 823365
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Iff0e8dae4bf80979868f5718427856d2efff7575
Reviewed-on: https://chromium-review.googlesource.com/1112066
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569896}
10 files changed