Implement override-based type inference for instance methods.

pkg/front_end/testcases/inference/infer_method_function_typed.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;
+
+// The `value` parameter for `B::x` has a type, so it should not be inferred
+// based on `A::x`.
+
+typedef int F();
+
+abstract class A {
+  void x(F value);
+}
+
+abstract class B extends A {
+  void x(value());
+}
+
+T f<T>() => null;
+
+g(B b) {
+  b. /*@target=B::x*/ x(/*@typeArgs=() -> dynamic*/ f());
+}
+
+main() {}