Fix dart2js_extra/23486_test

BUG=
R=floitsch@google.com

Review URL: https://codereview.chromium.org//1229253002.

tests/compiler/dart2js_extra/23486_test.dart

@@ -33,6 +33,6 @@ class D extends C {
 main() {
   Expect.throws(new A().m);          /// 01: continued
   Expect.throws(() => new D.name()); /// 02: continued
-  Expect.throws(() => (p).x);        /// 03: static type warning
+  Expect.throws(() => (p).x);        /// 03: compile-time error
 }
 

tests/compiler/dart2js_extra/dart2js_extra.status

@@ -11,8 +11,6 @@ no_such_method_test: Fail # Wrong Invocation.memberName.
 constant_javascript_semantics4_test: Fail, OK
 mirrors_used_closure_test: Fail # Issue 17939
 
-23486_test/03: Fail # TODO(johnni): please update test, fix dart2js, or create issue.
-
 [ $compiler == dart2js && $runtime == jsshell ]
 mirror_printer_test: Pass, Slow # Issue 16473