[RootLayerScrolls] Refactor scrollbar mode logic out of LocalFrameView

LocalFrameView no longer needs scrollbar modes. Also, move the autosize
scrollbar mode logic in LayoutView. LayoutView::CalculateScrollbarModes
is now the source of truth.

BUG=823365
R=pdr@chromium.org,skobes@chromium.org

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ie7bee820d189403c50d0b18d76bc14854e2998b8
Reviewed-on: https://chromium-review.googlesource.com/1117772
Commit-Queue: Stefan Zager <szager@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571238}
10 files changed