Change Aura overlay scrollbars from solid color to painted scrollbars.
With this change, the Aura overlay scrollbars are now painted by the native
theme. If the scroller is composited, these scrollbars will now be uploaded to
the compositor as PaintedScrollbarLayers rather than SolidColorScrollbarLayers.
Additionally, many of the MD scrollbar constants and properties are scattered
around the code. This patch moves them into a single location in
ui/native_theme. I've also updated the values to match the latest spec.
Follow-up patches will make use of these values from the compositor.
BUG=592098, 652520
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel
Review-Url: https://chromiumcodereview.appspot.com/2421913002
Cr-Commit-Position: refs/heads/master@{#426191}
15 files changed
