WebUI Dark Mode: update cr-toggle colors

Screenshots: https://imgur.com/a/i2uuR4y
Specs: https://docs.google.com/presentation/d/1kJoBzf_HGYK-_FAJPAjD67TW8224dCPLA6dAhlDmysk/edit?ts=5c363f50#slide=id.g3228466bab_0_40

R=dpapad@chromium.org
BUG=883049

Change-Id: I7e32f536f0b55f90320773aa1b53a7f392e5b985
Reviewed-on: https://chromium-review.googlesource.com/c/1426088
Commit-Queue: Dan Beam <dbeam@chromium.org>
Auto-Submit: Dan Beam <dbeam@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624859}
1 file changed