Get rid of obsolete unchecked accessors.

src/json-parser.h

Index: src/json-parser.h
diff --git a/src/json-parser.h b/src/json-parser.h
index 0c26c184ee806e84ced0ff011d6e5a087770cc2d..9aa42013f9650fc070515f8c1d311c0976e4ea02 100644
--- a/src/json-parser.h
+++ b/src/json-parser.h
@@ -628,11 +628,11 @@ Handle<String> JsonParser<seq_ascii>::ScanJsonString() {
     uint32_t count = 1;
     while (true) {
       Object* element = symbol_table->KeyAt(entry);
-      if (element == isolate()->heap()->raw_unchecked_undefined_value()) {
+      if (element == isolate()->heap()->undefined_value()) {
         // Lookup failure.
         break;
       }
-      if (element != isolate()->heap()->raw_unchecked_the_hole_value() &&
+      if (element != isolate()->heap()->the_hole_value() &&
           String::cast(element)->IsAsciiEqualTo(string_vector)) {
         // Lookup success, update the current position.
         position_ = position;