Rollback of r13728 in 3.17 branch.

src/json-parser.h

Index: src/json-parser.h
diff --git a/src/json-parser.h b/src/json-parser.h
index 8d9dddac664220fea3c856f7ebce09f7db17e63e..22f4c7042178e0c383713d5ebae6256f72767977 100644
--- a/src/json-parser.h
+++ b/src/json-parser.h
@@ -291,6 +291,7 @@ Handle<Object> JsonParser<seq_ascii>::ParseJsonValue() {
 // Parse a JSON object. Position must be right at '{'.
 template <bool seq_ascii>
 Handle<Object> JsonParser<seq_ascii>::ParseJsonObject() {
+  Handle<Object> prototype;
   Handle<JSObject> json_object =
       factory()->NewJSObject(object_constructor(), pretenure_);
   ASSERT_EQ(c0_, '{');
@@ -345,17 +346,22 @@ Handle<Object> JsonParser<seq_ascii>::ParseJsonObject() {
       Handle<Object> value = ParseJsonValue();
       if (value.is_null()) return ReportUnexpectedCharacter();
 
-      if (JSObject::TryTransitionToField(json_object, key)) {
-        int index = json_object->LastAddedFieldIndex();
-        json_object->FastPropertyAtPut(index, *value);
+      if (key->Equals(isolate()->heap()->Proto_symbol())) {
+        prototype = value;
       } else {
-        JSObject::SetLocalPropertyIgnoreAttributes(
-            json_object, key, value, NONE);
+        if (JSObject::TryTransitionToField(json_object, key)) {
+          int index = json_object->LastAddedFieldIndex();
+          json_object->FastPropertyAtPut(index, *value);
+        } else {
+          JSObject::SetLocalPropertyIgnoreAttributes(
+              json_object, key, value, NONE);
+        }
       }
     } while (MatchSkipWhiteSpace(','));
     if (c0_ != '}') {
       return ReportUnexpectedCharacter();
     }
+    if (!prototype.is_null()) SetPrototype(json_object, prototype);
   }
   AdvanceSkipWhitespace();
   return json_object;