Remove the HasOwnBackingButPaintsIntoAncestor compositing state.

LayoutTests/platform/linux/compositing/backing/no-backing-for-clip-overlap-expected.txt

 This layer should not have backing store.
 This layer should have backing store.
 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "children": [
         {
           "position": [8, 8],
           "bounds": [342, 182],
+          "drawsContent": true,
           "children": [
             {
               "position": [1, 1],
               "bounds": [340, 180],
               "children": [
                 {
                   "position": [30, 50],
                   "bounds": [100, 100],
                   "contentsOpaque": true,
                   "drawsContent": true,
@@ skipping 21 matching lines @@
                 }
               ]
             }
           ]
         }
       ]
     }
   ]
 }