Convert more tests into text-based-repaint tests

LayoutTests/platform/mac/fast/repaint/fixed-element-repaint-after-compositing-update-expected.txt

-This test checks that we correctly invalidate a shifted fixed positioned element overlapping another fixed positioned element.
-
-For this test, there should be only one green square below.
-
 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "children": [
         {
           "children": [
@@ skipping 10 matching lines @@
                 [0, 0, 100, 100]
               ]
             }
           ]
         }
       ]
     }
   ]
 }