Set MethodInvocation.interfaceTarget during type inference.

pkg/front_end/testcases/inference/static_method_tear_off.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;
 
-const /*@topType=f(String) -> int*/ v = C.f;
+const /*@topType=C::f(String) -> int*/ v = C.f;
 
 class C {
   static int f(String s) => null;
 }