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

third_party/WebKit/LayoutTests/platform/linux/paint/invalidation/4776765-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV",
           "rect": [7, 43, 786, 62],
           "reason": "outline"
         },
         {
           "object": "LayoutBlockFlow DIV id='div'",
           "rect": [8, 84, 784, 20],
           "reason": "layoutObject insertion"
         },
         {
-          "object": "LayoutBR BR",
+          "object": "LayoutBlockFlow DIV id='div'",
           "rect": [7, 83, 3, 21],
           "reason": "invalidate paint rectangle"
         },
         {
-          "object": "LayoutBR BR",
+          "object": "LayoutBlockFlow DIV id='div'",
           "rect": [7, 83, 3, 21],
           "reason": "invalidate paint rectangle"
         },
         {
-          "object": "LayoutBR BR",
+          "object": "LayoutBlockFlow DIV id='div'",
           "rect": [7, 83, 3, 21],
           "reason": "invalidate paint rectangle"
         },
         {
-          "object": "LayoutBR BR",
+          "object": "LayoutBlockFlow DIV id='div'",
           "rect": [7, 63, 3, 21],
           "reason": "invalidate paint rectangle"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "Caret",
       "reason": "invalidate paint rectangle"
@@ skipping 26 matching lines @@
       "object": "LayoutBR BR",
       "reason": "layoutObject insertion"
     },
     {
       "object": "InlineTextBox '\n'",
       "reason": "layoutObject insertion"
     }
   ]
 }