GitLab

by transferring ownership of a layer mask to the associated layer.

BUG=235563
TEST=Manual: when closing an Ash tray menu or tray notification, watch corners
     to make sure they remain rounded.
R=piman@chromium.org, msw@chromium.org, mukai@chromium.org, skuhne@chromium.org

Review URL: https://codereview.chromium.org/25961002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239930 0039d316-1c4b-4281-b951-d872f2087c98