Prevent cc:TextureLayer from calling AcquireLayerTexture when using mailboxes

BUG=315170
R=danakj@chromium.org, enne@chromium.org, piman@chromium.org

Review URL: https://codereview.chromium.org/69933014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235241 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235241