cc: Free Mailbox on TextureLayerImpl::ReleaseResources

Add unit tests to run through this code path

BUG=239864

Review URL: https://codereview.chromium.org/140693015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246690 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246690