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chromium/third_party/blink/web_tests/external/wpt/content-security-policy/navigate-to/support/delayed_frame.py 

import time
def main(request, response):
    time.sleep(1)
    headers = [(b"Content-Type", b"text/html")]
    return headers, u'''
<!DOCTYPE html>
<head>
</head>
<body>
    DELAYED FRAME
</body
'''