The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/992fa8feb97734b7f1facce0cd5feffbb98d15f6

commit 992fa8feb97734b7f1facce0cd5feffbb98d15f6
Author: estade <estade@chromium.org>
Date: Thu Mar 16 17:09:06 2017

Remove pre-MD code from SystemTrayBubble.

Delete TrayPopupItemContainer class, which was only used for adding a
hover effect that we don't want/use in MD.

BUG= 687802 

Review-Url: https://codereview.chromium.org/2758433002
Cr-Commit-Position: refs/heads/master@{#457462}

[modify] https://crrev.com/992fa8feb97734b7f1facce0cd5feffbb98d15f6/ash/BUILD.gn
[modify] https://crrev.com/992fa8feb97734b7f1facce0cd5feffbb98d15f6/ash/common/system/chromeos/audio/volume_view.cc
[modify] https://crrev.com/992fa8feb97734b7f1facce0cd5feffbb98d15f6/ash/common/system/tray/system_tray_bubble.cc
[modify] https://crrev.com/992fa8feb97734b7f1facce0cd5feffbb98d15f6/ash/common/system/tray/system_tray_unittest.cc
[delete] https://crrev.com/ed9e4bf5f9558fe1f3d30a92606d263b4f9a2d1a/ash/common/system/tray/tray_popup_item_container.cc
[delete] https://crrev.com/ed9e4bf5f9558fe1f3d30a92606d263b4f9a2d1a/ash/common/system/tray/tray_popup_item_container.h