UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.113 Safari/537.36

Steps to reproduce the problem:
start chrome in command line:
chrome --headless --disable-gpu --remote-debugging-port=9222 --disable-xssauditor --disable-client-side-phishing-detection --disable-sync --disable-web-resources

server the html code below on the local server.

	<div style="display:none"><form action="http://www.qq.com" method="post" name="popup" target="_blank"><input type="submit" style="display:none"/></form></div>

	<script type="text/javascript">
		document.getElementsByName("popup")[0].submit();
	</script>

run python code below.

	from websocket import create_connection
	import requests

	tab = requests.get("http://127.0.0.1:9222/json/new").json()
	tab_ws_url = tab['webSocketDebuggerUrl']

	ws = create_connection(tab_ws_url)
	ws.settimeout(5)

	ws.send(json.dumps({
	    "method": "Page.navigate",
	    "id": 2,
	    "params": {"url": "http://127.0.0.1:8000/untitled.html"}
	}))

	while True:
	    try:
	        data = ws.recv()
	        print(json.loads(data))
	    except WebSocketTimeoutException:
	        break

	requests.get("http://127.0.0.1:9222/json/close/{}".format(tab['id']))

3. see opened tabs with curl.

    curl http://127.0.0.1/json

I see it will auto open a tab when meets popups in headless mode. but starts without headless mode, it will auto block popups. like below.

so I want to auto block popups in headless mode, that means not open a new tab in headless mode or let me know what tab is opened.

I tried enable Target.setDiscoverTargets and monitor the Target.targetCreated but it will recv all opened tabs before.

What is the expected behavior?
don't open popup window in headless mode or let me known what new window is opened.

What went wrong?
ad window popups when in headless mode.

Did this work before? No 

Chrome version: 60.0.3112.113  Channel: stable
OS Version: OS X 10.12.6
Flash Version: Shockwave Flash 26.0 r0

thanks.