Revert "Remove U+180E from whitespace in js_runtime and tests"

tests/lib/math/math_parse_double_test.dart

Index: tests/lib/math/math_parse_double_test.dart
diff --git a/tests/lib/math/math_parse_double_test.dart b/tests/lib/math/math_parse_double_test.dart
index 9b122a737797d7c4de6396dd715aa6a6871e3fdd..666a9e5041233035f5993e6a504ec82e0da2748a 100644
--- a/tests/lib/math/math_parse_double_test.dart
+++ b/tests/lib/math/math_parse_double_test.dart
@@ -26,6 +26,7 @@ void runTest(double expected, String input) {
   Expect.equals(expected, double.parse("\xA0 +$input\xA0 "));
   Expect.equals(expected, double.parse("+$input\xA0 "));
   Expect.equals(expected, double.parse("\u205F $input\u205F "));
+  Expect.equals(expected, double.parse(" \u180E$input"));
   Expect.equals(expected, double.parse("$input \u2006"));
   Expect.equals(expected, double.parse("\u1680 +$input\u1680 "));
   Expect.equals(-expected, double.parse("-$input"));