[Gardening] Try skipping image-backgrounds-not-antialiased on Mac OS 10.7 (Lion)

Let's see, whether would it help webkit_tests to complete.

BUG=524248

git-svn-id: svn://svn.chromium.org/blink/trunk@201246 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/TestExpectations

@@ -1550,3 +1550,5 @@ crbug.com/524804 [ Win10 ] animations/svg-attribute-interpolation/svg-xChannelSe
 crbug.com/524826 [ Win10 ] compositing/squashing/squashing-reflection-disallowed.html [ Pass Timeout ]
 
 crbug.com/525065 webaudio/audionode-disconnect-audioparam.html [ Failure Pass ]
+
+crbug.com/524248 [ Lion ] paint/images/image-backgrounds-not-antialiased.html [ Skip ]