Previously, the focus highlights for the cursor, caret, and focus would fade out when not changing, but they're not doing that anymore.

I bisected to this change below. It's been broken for a long time so not urgent, but it would be nice to figure out why it broke and get back to the previous behavior.


Create a generic parent class for focus_ring_layer.

This will allow other types of accessibility layers to be drawn
that differ from the Focus Ring. Specifically, a highlight layer
is going to be added that depends on this new class, to enable
per-word highlighting in Select-to-Speak.

This is purely a refactor, with no functionality changes.

Bug:  676451 
Change-Id: I73c03cc022359f1cca8c5443b63a659dbb104775
Reviewed-on: https://chromium-review.googlesource.com/756281
Commit-Queue: Katie D <katie@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514741}