Add type inference of annotations.

pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /*@testedFeatures=inference*/
 library test;
 
 class Foo {
   const Foo(List<String> l);
-  const Foo.named(List<String> l);
 }
 
-@Foo(/*@typeArgs=String*/ const [])
-class Bar {}
+void test() {
+  void f(@Foo(/*@typeArgs=String*/ const []) /*@type=dynamic*/ x) {}
+  var /*@type=(dynamic) -> Null*/ x = /*@returnType=Null*/ (/*@type=dynamic*/ @Foo(/*@typeArgs=String*/ const [])
+      x) {};
+}
 
-@Foo.named(/*@typeArgs=String*/ const [])
-class Baz {}
+main() {}