Fix caret paint invalidation when moving between blocks

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

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV",
@@ skipping 12 matching lines @@
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow DIV",
       "reason": "border box change"
     },
     {
+      "object": "Caret",
+      "reason": "caret"
+    },
+    {
       "object": "LayoutBlockFlow DIV id='div'",
       "reason": "layoutObject insertion"
     },
     {
       "object": "RootInlineBox",
       "reason": "layoutObject insertion"
     },
     {
       "object": "Caret",
       "reason": "caret"
     },
     {
       "object": "LayoutBR BR",
       "reason": "layoutObject insertion"
     },
     {
       "object": "InlineTextBox '\n'",
       "reason": "layoutObject insertion"
     }
   ]
 }