I see the spec also gives regular buttons a slight shadow on hover.

Fixing this is actually a bit involved. This happens because we disable ink drops on Mac, and the shadows happen to use the layer we add for ink drops. For Mac, we'll need to add a layer and draw our shadow to it without having the ink drops.

patricialor@, please have a look at this :)

M-56 clearly didn't happen.

I don't know how to triage MacViews in depth, so not changing owner/priority.  This hasn't been touched in a while; please retriage.

Taking this on. I think a while ago we did some architectural changes so that the ink drop layer is present on Mac but unused, which means we can draw the shadow there properly now.

The NextAction date has arrived: 2017-08-04

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dde3e544e6852a99205b605c80778e5b0096ebee

commit dde3e544e6852a99205b605c80778e5b0096ebee
Author: Elly Fong-Jones <ellyjones@chromium.org>
Date: Wed Aug 09 15:18:15 2017

views: show hover shadows for buttons on Mac

Button hover shadows are implemented as part of the ink drop code, which has a
separate layer that it uses to draw these kinds of effects. The Mac code thus
far has stubbed out ink drops, but that prevents the effects layer from being
created, which prevents drop shadows from being drawn. This change causes
the ink drop code to still create the effects layer, but to draw the actual
ink drop itself with zero opacity on button press, so other effects that
depend on the ink drop code still work.

Note that controls which explicitly set their ink drop opacity (ie, don't just
use the default) will still get ink drops *even if* PlatformStyle disables
them. At the moment these controls are almost entirely ChromeOS-specific, but
a more principled approach to disabling ink drops for Mac might be in order
later.

Bug:  654783 
Change-Id: I4caeabc6511a22fe3cdd457d0c78c77798a14f56
Reviewed-on: https://chromium-review.googlesource.com/602253
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Ben Ruthig <bruthig@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492987}
[modify] https://crrev.com/dde3e544e6852a99205b605c80778e5b0096ebee/ui/views/animation/ink_drop_host_view.cc
[modify] https://crrev.com/dde3e544e6852a99205b605c80778e5b0096ebee/ui/views/controls/button/toggle_button_unittest.cc

 Issue 755847  has been merged into this issue.