Merge request - fixes dart2js async problems.

tests/language/language.status

Index: tests/language/language.status
===================================================================
--- tests/language/language.status	(revision 43839)
+++ tests/language/language.status	(working copy)
@@ -55,7 +55,9 @@
 async_await_syntax_test/d10a: CompileTimeError # Issue 21404
 
 [ $compiler == none || ($compiler == dart2dart && $builder_tag != new_backend) ]
+async_throw_in_catch_test: Crash # Issue 22445, 22446
 compile_time_constant_c_test/01: Fail # Issue 21000
+asyncstar_throw_in_catch_test: CompileTimeError # Issue 21404
 async_await_syntax_test/a03a: CompileTimeError # Issue 21404
 async_await_syntax_test/a03b: CompileTimeError # Issue 21404
 async_await_syntax_test/a11d: CompileTimeError # Issue 21404
@@ -66,6 +68,8 @@
 sync_generator3_test/test2: Fail # Issue 22300
 
 [ $compiler == none && ($runtime == drt || $runtime == dartium|| $runtime == ContentShellOnAndroid) ]
+async_throw_in_catch_test: Timeout # Issue 22445, 22446
+asyncstar_throw_in_catch_test: RuntimeError # Issue 21404
 async_await_syntax_test/a03a: RuntimeError # Issue 21404
 async_await_syntax_test/a03b: RuntimeError # Issue 21404
 async_await_syntax_test/a09a: RuntimeError # Issue 21404