RegExp.prototype is an ordinary object.

test/test262/test262.status

 # Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 137 matching lines @@
   'built-ins/Object/getOwnPropertyDescriptor/15.2.3.3-4-212': [FAIL],
   'built-ins/Object/getOwnPropertyDescriptor/15.2.3.3-4-213': [FAIL],
   'built-ins/Object/getOwnPropertyDescriptor/15.2.3.3-4-214': [FAIL],
   'built-ins/Object/getOwnPropertyDescriptor/15.2.3.3-4-215': [FAIL],
   'built-ins/RegExp/prototype/global/15.10.7.2-1': [FAIL],
   'built-ins/RegExp/prototype/global/15.10.7.2-2': [FAIL],
   'built-ins/RegExp/prototype/global/S15.10.7.2_A9': [FAIL],
   'built-ins/RegExp/prototype/ignoreCase/15.10.7.3-1': [FAIL],
   'built-ins/RegExp/prototype/ignoreCase/15.10.7.3-2': [FAIL],
   'built-ins/RegExp/prototype/ignoreCase/S15.10.7.3_A9': [FAIL],
-  'built-ins/RegExp/prototype/lastIndex/15.10.7.5-1': [FAIL],
-  'built-ins/RegExp/prototype/lastIndex/15.10.7.5-2': [FAIL],
   'built-ins/RegExp/prototype/multiline/15.10.7.4-1': [FAIL],
   'built-ins/RegExp/prototype/multiline/15.10.7.4-2': [FAIL],
   'built-ins/RegExp/prototype/multiline/S15.10.7.4_A9': [FAIL],
   'built-ins/RegExp/prototype/source/15.10.7.1-1': [FAIL],
   'built-ins/RegExp/prototype/source/15.10.7.1-2': [FAIL],
   'built-ins/RegExp/prototype/source/S15.10.7.1_A9': [FAIL],
 
   # https://code.google.com/p/v8/issues/detail?id=4243
   'built-ins/Promise/race/S25.4.4.3_A3.1_T2': [FAIL],
   'built-ins/Promise/reject/S25.4.4.4_A3.1_T1': [FAIL],
 
   # https://code.google.com/p/v8/issues/detail?id=4119
   'built-ins/RegExp/15.10.4.1-1': [FAIL],
   'built-ins/RegExp/S15.10.3.1_A2_T1': [FAIL],
   'built-ins/RegExp/S15.10.3.1_A2_T2': [FAIL],
   'built-ins/RegExp/S15.10.4.1_A2_T1': [FAIL],
   'built-ins/RegExp/S15.10.4.1_A2_T2': [FAIL],
   'built-ins/RegExp/call_with_non_regexp_same_constructor': [FAIL],
   'built-ins/RegExp/from-regexp-like-short-circuit': [FAIL],
   'built-ins/RegExp/from-regexp-like': [FAIL],
   'built-ins/RegExp/from-regexp-like-flag-override': [FAIL],
   'built-ins/RegExp/from-regexp-like-get-source-err': [FAIL],
   'built-ins/RegExp/from-regexp-like-get-flags-err': [FAIL],
   'built-ins/RegExp/from-regexp-like-get-ctor-err': [FAIL],
   'built-ins/RegExp/call_with_regexp_not_same_constructor': [FAIL],
 
-  # https://code.google.com/p/v8/issues/detail?id=4003
-  'built-ins/RegExp/prototype/15.10.6': [FAIL],
+  # https://code.google.com/p/v8/issues/detail?id=4528
+  'built-ins/RegExp/prototype/source/S15.10.7.1_A8': [FAIL],
+  'built-ins/RegExp/prototype/source/S15.10.7.1_A10': [FAIL],
+  'built-ins/RegExp/prototype/global/S15.10.7.2_A8': [FAIL],
+  'built-ins/RegExp/prototype/global/S15.10.7.2_A10': [FAIL],
+  'built-ins/RegExp/prototype/ignoreCase/S15.10.7.3_A8': [FAIL],
+  'built-ins/RegExp/prototype/ignoreCase/S15.10.7.3_A10': [FAIL],
+  'built-ins/RegExp/prototype/multiline/S15.10.7.4_A8': [FAIL],
+  'built-ins/RegExp/prototype/multiline/S15.10.7.4_A10': [FAIL],
 
   # https://code.google.com/p/v8/issues/detail?id=4006
   'built-ins/String/prototype/S15.5.4_A1': [FAIL],
   'built-ins/String/prototype/S15.5.4_A2': [FAIL],
   'built-ins/String/prototype/S15.5.4_A3': [FAIL],
   'language/expressions/property-accessors/S11.2.1_A4_T5': [FAIL],
 
   # https://code.google.com/p/v8/issues/detail?id=4245
   'built-ins/String/prototype/split/S15.5.4.14_A2_T37': [FAIL],
 
@@ skipping 505 matching lines @@
 
   # BUG(3251225): Tests that timeout with --nocrankshaft.
   'built-ins/decodeURI/S15.1.3.1_A2.4_T1': [SKIP],
   'built-ins/decodeURI/S15.1.3.1_A2.5_T1': [SKIP],
   'built-ins/decodeURIComponent/S15.1.3.2_A2.4_T1': [SKIP],
   'built-ins/decodeURIComponent/S15.1.3.2_A2.5_T1': [SKIP],
   'built-ins/encodeURI/S15.1.3.3_A2.3_T1': [SKIP],
   'built-ins/encodeURIComponent/S15.1.3.4_A2.3_T1': [SKIP],
 }],  # 'arch == arm or arch == mipsel or arch == mips or arch == arm64'
 ]