GitLab

Make UnifiedSliderButton as ImageButton only and decorate it with
kIconButtonSmallOrMedium.

Bug: 1133748
Change-Id: Ic154c6ef63770d66ae4d09eb4b3cf1190be056cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441190
Commit-Queue: Min Chen <minch@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813032}