Add Null class to dart:core.

tests/language/language.status

Index: tests/language/language.status
diff --git a/tests/language/language.status b/tests/language/language.status
index 97d31b4bd5e59924c67fcdf62062ab5d9b62ce0a..0763f1473a599f680708642e1481d4f2eb7101a3 100644
--- a/tests/language/language.status
+++ b/tests/language/language.status
@@ -299,3 +299,9 @@ import_core_prefix_test: Pass
 prefix22_test: Pass
 invocation_mirror_test: Fail, OK # hardcoded names.
 super_call4_test: Fail, OK # hardcoded names.
+
+[ $compiler == dart2js || $compiler == dart2dart]
+null_test/03: Fail    # Issue 12445.
+
+[$ compiler == dart2js]
+null_test/none: Fail  # Issue 12482

[ahe, 2013/08/15 11:16:46]

This really means that this test isn't passing on dart2js.

So there is no test coverage of this change in dart2js. I consider that a big
problem, but I'm not going to artificially increase the priority of reflecting
on null. So I'd really appreciate if you could move the mirrors part to a
different test.

[Lasse Reichstein Nielsen, 2013/08/15 13:06:10]

The mirror part has been moved.
Most of it was already in lib/mirrors/null_test.