Mailbox support for texture layers.
A callback object is passed along with the mailbox name to the layer. This callback is triggered with a sync point to signal when the mailbox is no longer in use by the compositor.
TextureLayerImpl packages a mailbox up as a resource on willDraw
and releases it when a new mailbox is ready for consumption or when the layer is destroyed.
BUG=123444
Review URL: https://chromiumcodereview.appspot.com/
11638028
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175529 0039d316-1c4b-4281-b951-d872f2087c98