Squashed 'WLContainerControllers/' changes from 7ec7048..730be36

730be36 Let content view controller control the visibility of toolbar.

git-subtree-dir: WLContainerControllers
git-subtree-split: 730be36d809a132dbbc8d9adb0bb34cb5477b79a
Merge commit '38612f1d6805fa8ed4000e583511bc7c6604f688'