VM crash - sending the same function twice in a message fails.

[lrhn]

Example code:
  import "dart:isolate";
  func(){}
  main() {
    var r = new RawReceivePort();
    r.handler = (v) {
      print(v[0] == v[1]);
      r.close();
    };
    r.sendPort.send([func, func]);
  }

This prints:
runtime/vm/object.h:4781: error: Handle check failed: saw Function 'main': static. expected Instance
Aborted (core dumped)

[iposva-google]

Set owner to @a-siva.
Added Accepted label.

[a-siva]

uploaded cl https://codereview.chromium.org/1004923002/ for review.

[a-siva]

Added Fixed label.