测试了一天，发现flash新版已经不支持在GET里面用自定义的URLRequestHeader了，必须要在POST里面才能用，日了，无语了。。。Get的话还是要用random string才能忽略浏览器的缓存啊。郁闷。
这样子又要回到squid里面设置rewrite来忽略query string了，ooxx。。。
Due to browser limitations, custom HTTP request headers are only supported for POST requests, not for GET requests.
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This restriction will be included in the next version of the Language Reference.