HTTPでWebサーバからレスポンスを受け取る

using UnityEngine;
using System.Collections;

public class Main : MonoBehaviour {
  public string url = "http://www.google.com";
  public string output = "(ここに結果を表示)";

  private GetViaHttp http;

  void Start() {
    http = GetComponent<GetViaHttp>();
  }

  void OnGUI() {
    // Button
    if(GUI.Button(new Rect(30, 30, 100, 30), "GET via HTTP")) {
      Debug.Log("GET!!!");
      StartCoroutine("GetUrl");
    }
    // TextArea for Output
    GUI.TextArea(new Rect(30, 70, 800, 600), output);
  }

	private IEnumerator GetUrl() {
      Debug.Log("Start2");
	    WWW www = new WWW(url);
	    yield return www;
	    Debug.Log(www.text);
      output = www.text;
	}
}