Add type inference for super method invocations.

pkg/front_end/testcases/classes.dart.direct.expect

 library;
 import self as self;
 import "dart:core" as core;
 
 class A extends core::Object {
   final field core::int x;
   final field core::int y;
   constructor •(core::int y) → void
     : self::A::y = y, self::A::x = 42, super core::Object::•()
     ;
   method method() → dynamic {
     core::print("A.method x: ${this.x} y: ${this.y}");
     core::print(this);
     core::print(this.runtimeType);
   }
 }
 class B extends self::A {
   constructor •(dynamic x) → void
     : super self::A::•(x)
     ;
   method method() → dynamic {
     core::print("B.method x: ${this.x} y: ${this.y}");
-    super.method();
+    super.{self::A::method}();
   }
 }
 static method main() → dynamic {
   self::A a = new self::A::•(87);
   self::B b = new self::B::•(117);
   a.method();
   b.method();
 }