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

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index d990dc53cdfb7834d8c18cd2b98723fc43166d6d..3122609da7628331237b1709ac47d8cfbb8e90f9 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -237,6 +237,9 @@ mirrors/mirrors_used_get_name2_test: RuntimeError
 convert/streamed_conversion_utf8_decode_test: Pass, Slow  # Issue 12029
 mirrors/mirrors_reader_test: Timeout, Slow, RuntimeError # Issue 16589
 
+[ $compiler == dart2js && $runtime == ff ]
+math/math_parse_double_test: Pass, RuntimeError # Issue 28983
+
 [ $runtime == chrome && $system == macos ]
 async/timer_isActive_test: Fail, Pass, Timeout # Issue 22696
 async/slow_consumer_test: Pass, Timeout # Issue 22696