Implement 'this' calls.

test/kernel/regression/this_invoke.dart.txt

 library;
 import self as self;
 import "dart:core" as core;
 
 class C extends core::Object {
   constructor •() → self::C
     : super core::Object::•();
-  method test() → dynamic {
-    self::use(invalid-expression);
-  }
+  method m(dynamic x) → dynamic
+    return this.call(x);
+  method call(dynamic x) → dynamic
+    return 42;
 }
-static method use(dynamic _) → dynamic
-  return null;
 static method main() → dynamic {
-  new self::C::•().test();
+  core::print(new self::C::•().m(42));
 }