Something else to consider, beyond adding support for deviceScaleFactor would be whether a mobile user agent should be sent when requesting with mobile viewport dimensions, and whether the same should be done for desktop. WP Rocket, for example, has different caches for mobile and desktop user agents, with device-specific optimizations applied. For non-responsive sites, it's common to send back entirely different HTML for desktop and mobile. So if we don't (eventually) also support full emulation then we won't get the expected results back.

Thinking about this some more, I think we should also have a --emulate-device (-e) option which allows you to pass a predefined device name which would then populate the viewportWindow. This would supply the deviceScaleFactor and set the user agent and all that. We can still also provide a --window-viewport argument to override the specific dimensions, or if we don't want to emulate anything.

@westonruter Those ideas sound good to me, we could explore them in separate PRs. Though this could also wait until we find an actual use-case that would require us to support those.

As it stands right now, specifying -w mobile won't necessarily result in what is expected since the pixel density won't be right and the user agent won't be sent as a mobile device, so I think it's important to support to get accurate results.

Follow up: #166