You'd think just "webkit", but the screenshots it shows me (and the issues it finds) are quite different to anything that I've seen via devtools device testing or using actual devices.
Is it maybe just an outdated version of webkit?
Without knowing what they're using it's hard to know how to fix the issues, and I feel they'll negatively affect my search index rankings if I don't.
tl;dr:
1- You are right, it is webkit, however, it is a pretty much A stripped down version of Chrome for Android
2- What you see is the default android browser, you can use
and look at "Android Browser" to see whether or not your design is supported by the "mobile view" in PageSpeed
Long Version:
my understanding is this:
1- The view-port you see in PageSpeed represents what a person using the default browser in Android phones would see.
2- The Default Android browser - AKA "WebView" -
is based on the same code as Chrome for Android version
However,
WebView does not have full feature parity with Chrome for Android
Source: Google