[regexp] Consider surrogate pairs when optimizing disjunctions

test/mjsunit/regress/regress-641091.js

Index: test/mjsunit/regress/regress-641091.js
diff --git a/test/mjsunit/regress/regress-641091.js b/test/mjsunit/regress/regress-641091.js
new file mode 100644
index 0000000000000000000000000000000000000000..33a98ef52cd3e7efc55aa6b407e2e9a121d36f2d
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+++ b/test/mjsunit/regress/regress-641091.js
@@ -0,0 +1,15 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+assertEquals(["🍤", "🍤"],
+             '🍤🍦🍋ππ🍋🍦🍤'.match(/🍤/ug));
+
+assertEquals(["🍤", "🍦", "🍦", "🍤"],
+             '🍤🍦🍋ππ🍋🍦🍤'.match(/🍤|🍦/ug));
+
+assertEquals(["🍤", "🍦", "🍋", "🍋", "🍦", "🍤"],
+             '🍤🍦🍋ππ🍋🍦🍤'.match(/🍤|🍦|🍋/ug));
+
+assertEquals(["🍤", "🍦", "🍋", "π", "π", "🍋", "🍦", "🍤"],
+             '🍤🍦🍋ππ🍋🍦🍤'.match(/🍤|🍦|π|🍋/ug));