Delete LocalFrameView::ScrollbarManager and scroll_corner_.

This removes methods and paths in LocalFrameView that depend directly on
scrollbar existence.  Since RLS, LocalFrameView never has scrollbars.

Bug: 823365
Change-Id: I691480e4cad9239f12c50aa868c5d13571d45b2f
Reviewed-on: https://chromium-review.googlesource.com/1097540
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566618}
8 files changed