Remove the HasOwnBackingButPaintsIntoAncestor compositing state.

LayoutTests/compositing/layer-creation/overlap-animation-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "children": [
         {
           "position": [8, 8],
           "bounds": [122, 242],
+          "drawsContent": true,
           "children": [
             {
               "position": [1, 1],
               "bounds": [120, 240],
               "children": [
                 {
                   "shouldFlattenTransform": false,
                   "children": [
                     {
                       "position": [10, 10],
@@ skipping 17 matching lines @@
                 }
               ]
             }
           ]
         }
       ]
     }
   ]
 }