Implement type inference of static invocations.

pkg/front_end/testcases/inference/inferred_type_invoke_method_via_interface.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 I {
   bool g() => true;
 }
 
 abstract class C implements I {}
 
 C f() => null;
 var /*@topType=bool*/ x = f(). /*@target=I::g*/ g();
+
+main() {}