Let's wait until M-56 has had a bit of time to bake in stable channel before doing this.

Also it would be good to address the handful of TODOs in palette_tray.cc. If any end up being more involved than just re-using existing code elsewhere in the system menu, feel free to spin off separate issues for those and tag them with Proj-MaterialDesign-CrOS.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/beba3d3c3694aef72793429f3f66ab236c541def

commit beba3d3c3694aef72793429f3f66ab236c541def
Author: estade <estade@chromium.org>
Date: Tue Apr 18 14:42:56 2017

Remove ash's MaterialDesignController.

Remove pre-MD code at the last couple of callsites.

BUG= 686245 
TBR=pkotwicz@chromium.org

Review-Url: https://codereview.chromium.org/2826593002
Cr-Commit-Position: refs/heads/master@{#465233}

[modify] https://crrev.com/beba3d3c3694aef72793429f3f66ab236c541def/ash/BUILD.gn
[delete] https://crrev.com/bc913634cadc4ac06b3637b2025129d1c513bf65/ash/material_design/material_design_controller.cc
[delete] https://crrev.com/bc913634cadc4ac06b3637b2025129d1c513bf65/ash/material_design/material_design_controller.h
[modify] https://crrev.com/beba3d3c3694aef72793429f3f66ab236c541def/ash/system/palette/palette_tray.cc
[modify] https://crrev.com/beba3d3c3694aef72793429f3f66ab236c541def/ash/system/status_area_widget.cc
[modify] https://crrev.com/beba3d3c3694aef72793429f3f66ab236c541def/ash/wm/overview/window_selector_item.cc
[modify] https://crrev.com/beba3d3c3694aef72793429f3f66ab236c541def/chrome/browser/ui/views/frame/immersive_mode_controller_ash.cc

spun off  Issue 717784