Remove RootLayerScrolling REF.

This removes the entry in runtime_enabled_features.json5 along with the
two remaining uses of it in LocalFrameView.

Bug: 823365
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ic220dc9dc67c658900619f7f89f83ffce226e4dd
Reviewed-on: https://chromium-review.googlesource.com/1073387
Commit-Queue: Steve Kobes <skobes@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561882}
4 files changed