Unity3D StartCoroutine 调用一个函数，该函数什么时候返回？

我知道Unity3D StartCoroutine调用了一个与StartCoroutine在同一线程上运行的函数，但是被调用的函数什么时候返回到原始调用者？

我在互联网上查找了一个很好的 Unity3D Coroutine 示例，但找不到完整的示例。有一个很好的解释 http://unitygems.com/coroutines/由 UnityGems 提供，但即使他们的示例也是不完整的。所以我写了自己的例子。

This:

using UnityEngine;
using System.Collections;
public class MainCamera: MonoBehaviour {
  void Start () {
    Debug.Log ("About to StartCoroutine");
    StartCoroutine(TestCoroutine());
    Debug.Log ("Back from StartCoroutine");
  }
  IEnumerator TestCoroutine(){
    Debug.Log ("about to yield return WaitForSeconds(1)");
    yield return new WaitForSeconds(1);
    Debug.Log ("Just waited 1 second");
    yield return new WaitForSeconds(1);
    Debug.Log ("Just waited another second");
    yield break;
    Debug.Log ("You'll never see this"); // produces a dead code warning
  }
}

产生以下输出：

About to StartCoroutine
about to yield return WaitForSeconds(1)
Back from StartCoroutine
Just waited 1 second
Just waited another second