UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36

Steps to reproduce the problem:
1. Run this command

C:\Program Files (x86)\Google\Chrome\Application>chrome   --disable-search-geolocation-disclosure  --disable-gpu --enable-logging --v=99 --headless  --disable-gpu  --screenshot="C:\temp\bestbuy.png" --window-size=320,568 --hide-scrollbars --useragent="Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A334 Safari/7534.48.3" http://www.bestbuy.com

2. Run this command

C:\Program Files (x86)\Google\Chrome\Application>chrome  --disable-gpu  --headless  --disable-gpu  --screenshot="C:\Temp\bing.png" --window-size=320,568 --hide-scrollbars --user-agent="Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A334 Safari/7534.48.3" http://www.bing.com

3. 

What is the expected behavior?
Screenshot file should always be generated.

For bestbuy no screenshot is generated

For bing.com a screenshot is generated too early (before the page load settles)

What went wrong?
No file is generated / the command hangs indefinitely
It also appears that the headless screenshot might be hanging because of the location prompt, too - not sure about that. See attached.  If I run without the disable-search-geolocation-disclosure flag and without the headless I see the attached screen 

Did this work before? N/A 

Does this work in other browsers? N/A

Chrome version: 65.0.3325.181  Channel: stable
OS Version: 10.0
Flash Version: 

The screenshot command works great for 95% of all sites.  For just a few it hangs like this, or (for example with www.bing.com) it grabs a screenshot to early - before the page has fully loaded.

If I test bestbuy without applying the mobile UA, it will generate a screenshot - it takes 20-30 seconds, but it does generate one.
 

Deleted: chomium screenshot non-headless location prompt.jpg 13.3 KB

	chomium screenshot non-headless location prompt.jpg 13.3 KB View Download

Deleted: chromium screenshot bing to early.png 7.0 KB

	chromium screenshot bing to early.png 7.0 KB View Download