Use anchor node, rather than current selected node, to check editability.

third_party/WebKit/LayoutTests/platform/mac/paint/invalidation/selection-after-delete-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV id='test'",
           "rect": [38, 74, 152, 110],
           "reason": "forced by layout"
         },
         {
           "object": "LayoutText #text",
           "rect": [39, 75, 123, 108],
           "reason": "layoutObject removal"
         },
         {
-          "object": "LayoutBR BR",
+          "object": "LayoutBlockFlow DIV id='test'",
           "rect": [38, 74, 3, 20],
           "reason": "invalidate paint rectangle"
         },
         {
-          "object": "LayoutBR BR",
+          "object": "LayoutBlockFlow DIV id='test'",
           "rect": [38, 74, 3, 20],
           "reason": "invalidate paint rectangle"
         },
         {
-          "object": "LayoutBR BR",
+          "object": "LayoutBlockFlow DIV id='test'",
           "rect": [38, 74, 3, 20],
           "reason": "invalidate paint rectangle"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutText #text",
       "reason": "layoutObject removal"
@@ skipping 22 matching lines @@
       "object": "LayoutBR BR",
       "reason": "forced by layout"
     },
     {
       "object": "InlineTextBox '\n'",
       "reason": "forced by layout"
     }
   ]
 }