Handle creating ParameterMirrors for the parameters of forwarding constructors.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index 6e283891f82f0e1170971c05f1e88dfd44682513..597d3aeb0aad4a5aaa9ce254dafd3e739ade71fd 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -94,6 +94,7 @@ mirrors/mirrors_test: RuntimeError # TODO(ahe): I'm working on fixing this.
 mirrors/mixin_test: RuntimeError # Issue 12464
 mirrors/mixin_application_test/none: RuntimeError # Issue 12464
 mirrors/parameter_test/none: RuntimeError # Issue 6490
+mirrors/parameter_of_mixin_app_constructor_test: RuntimeError # Issue 6490
 mirrors/private_symbol_test: CompileTimeError # Issue 13597
 mirrors/proxy_type_test: RuntimeError # Issue 13842
 mirrors/redirecting_factory_test/none: RuntimeError # Issue 6490
@@ -257,7 +258,7 @@ mirrors/symbol_validation_test: RuntimeError # Issue 13596
 
 async/timer_not_available_test: SkipByDesign # only meant to test when there is no way to implement timer (currently only in d8)
 
-mirrors/immutable_collections_test: Fail # Issue 17823
+##### mirrors/immutable_collections_test: Fail # Issue 17823
 
 [ $compiler == none && ( $runtime == drt || $runtime == dartium || $runtime == ContentShellOnAndroid) ]
 async/schedule_microtask6_test: Fail # Issue 10910