Support for Null as bottom in dart2js

tests/language/language.status

Index: tests/language/language.status
diff --git a/tests/language/language.status b/tests/language/language.status
index 0cf467087029bbd835c0be8e3d53045b0d83ef27..3fefdf6df854b783ed9f9a6ec7da64996907843a 100644
--- a/tests/language/language.status
+++ b/tests/language/language.status
@@ -5,9 +5,22 @@
 # This directory contains tests that are intended to show the
 # current state of the language.
 
+[ $compiler == none || $compiler == app_jit ]
+null_is_bottom_test/22: RuntimeError # Issue 28025
+null_is_bottom_test/34: RuntimeError # Issue 28025
+
+
 [ $compiler == none || $compiler == precompiler || $compiler == app_jit ]
 tearoff_constructor_basic_test: Skip # Crashes in checked mode -- hausner investigating
 generic_methods_type_expression_test: RuntimeError # Issue 25869
+null_is_bottom_test/05: RuntimeError # Issue 28025
+null_is_bottom_test/07: RuntimeError # Issue 28025
+null_is_bottom_test/20: RuntimeError # Issue 28025
+null_is_bottom_test/25: RuntimeError # Issue 28025
+null_is_bottom_test/27: RuntimeError # Issue 28025
+null_is_bottom_test/32: RuntimeError # Issue 28025
+null_is_bottom_test/37: RuntimeError # Issue 28025
+null_is_bottom_test/39: RuntimeError # Issue 28025
 
 # This is OK for now, but we may want to change the semantics to match the test.
 async_star_pause_test: Fail, OK
@@ -60,6 +73,11 @@ generic_methods_new_test: Pass # Issue 25869
 generic_local_functions_test: Pass # Issue 25869
 generic_functions_test: Pass # Issue 25869
 generic_methods_generic_function_parameter_test: Pass # Issue 25869
+null_is_bottom_test/03: RuntimeError # Issue 28025
+null_is_bottom_test/18: RuntimeError # Issue 28025
+null_is_bottom_test/23: RuntimeError # Issue 28025
+null_is_bottom_test/30: RuntimeError # Issue 28025
+null_is_bottom_test/35: RuntimeError # Issue 28025
 
 [ ($compiler == none || $compiler == precompiler || $compiler == app_jit) && ($runtime == vm || $runtime == dart_precompiled) ]