Allow identifier code points from supplementary multilingual planes.

test/mjsunit/parse-surrogates.js

Index: test/mjsunit/parse-surrogates.js
diff --git a/test/mjsunit/es6/regress/regress-crbug-346141.js b/test/mjsunit/parse-surrogates.js
similarity index 52%
copy from test/mjsunit/es6/regress/regress-crbug-346141.js
copy to test/mjsunit/parse-surrogates.js
index 2b9655e174459088401996b884c4a5d7e02eb919..5ed9b524ce2e0510ce67a8ea74dbc7eb2c77f1a1 100644
--- a/test/mjsunit/es6/regress/regress-crbug-346141.js
+++ b/test/mjsunit/parse-surrogates.js
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-var s = Symbol()
-var o = {}
-o[s] = 2
-o[""] = 3
-Object.getOwnPropertySymbols(o)
+// Test that the parser throws on unmatched surrogates.
+assertThrows("var \uD801\uABCD;", SyntaxError);
+assertThrows("'\\u000\uD801\uABCD'", SyntaxError);