Make TypedefMirror a direct descendant of TypeMirror.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index b5afe9bb4d4e35a35e999d49752a8832b8d0c0e5..6b801d3a05a1d6bf6f7990476b87dce4c373a662 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -179,6 +179,7 @@ mirrors/generic_function_typedef_test: RuntimeError # Issue 12282
 mirrors/generic_f_bounded_test: RuntimeError # Issue 14000
 mirrors/immutable_collections_test: RuntimeError # Issue 14027
 mirrors/symbol_validation_test: RuntimeError # Issue 13596
+mirrors/typevariable_mirror_metadata_test/none: RuntimeError # Issue 12282
 
 async/timer_isolate_test: Skip # See Issue 4997
 async/timer_not_available_test: SkipByDesign # only meant to test when there is no way to implement timer (currently only in d8)
@@ -210,6 +211,7 @@ mirrors/generic_mixin_test/none: Fail # Issue 13432
 mirrors/invoke_named_test/none: Fail # http://dartbug.com/13612
 mirrors/generic_f_bounded_mixin_application_test: Fail # Issue 14116
 mirrors/generic_interface_test/none: Fail # Inexpressible in multitest
+mirrors/typevariable_mirror_metadata_test/none: Fail # Issue 13093
 
 [ $compiler == dart2analyzer ]
 mirrors/typedef_test/none: Fail # Issue 13093
@@ -220,6 +222,7 @@ mirrors/generic_mixin_test/none: Fail # Issue 13432
 mirrors/invoke_named_test/none: Fail # http://dartbug.com/13612
 mirrors/generic_f_bounded_mixin_application_test: Fail # Issue 14116
 mirrors/generic_interface_test/none: Fail # Inexpressible in multitest
+mirrors/typevariable_mirror_metadata_test/none: Fail # Issue 13093
 
 [ $compiler == none && $runtime == dartium ]
 async/schedule_microtask5_test: Pass, Timeout # Issue 13719: Please triage this failure.