Mark Firefox/jsshell as failing on double_parse_test.

tests/corelib/corelib.status

Index: tests/corelib/corelib.status
diff --git a/tests/corelib/corelib.status b/tests/corelib/corelib.status
index 743832bd31190a24d271d8ebee6031b452c370c5..f1be4a96ddd0ceaab6b129e39af7c067b4bed31c 100644
--- a/tests/corelib/corelib.status
+++ b/tests/corelib/corelib.status
@@ -92,6 +92,12 @@ core_runtime_types_test: Pass, Fail # Issue 20525
 
 [ $runtime == ff || $runtime == jsshell ]
 unicode_test: Fail
+# Firefox takes advantage of the ECMAScript number parsing cop-out clause
+# (presumably added to allow Mozilla's existing behavior)
+# and only looks at the first 20 significant digits.
+# The Dart VM and the other ECMAScript implementations follow the correct
+# IEEE-754 rounding algorithm.
+double_parse_test: Fail, OK
 
 [ $runtime == ff || $runtime == jsshell || $runtime == safari || $runtime == safarimobilesim ]
 double_round3_test: Fail, OK # Runtime rounds 0.49999999999999994 to 1.