So I have found that rather than messing with the delta values, the simplest way to solve the problem would be to find a clean way to
detect if the browser was Chromium or not. I found that chromium browsers have a property called windows.chrome which on console logging, looks something like this:
{
app: {
isInstalled: false,
InstallState: {
DISABLED: disabled,
INSTALLED: installed,
NOT_INSTALLED: not_installed
},
RunningState: {
CANNOT_RUN: cannot_run,
READY_TO_RUN: ready_to_run,
RUNNING: running
}
},
appPinningPrivate: {}
}
Whereas in firefox, logging that property returns undefined. I had searched to see if there were ways that the window.chrome property could be faked (since the navigator.userAgent could be faked) but I couldnt find anything regarding that. Whats more, Edge, Opera, Brave and Chrome all support this property as per https://stackoverflow.com/a/13348618
So the current fix just adds the windows.chrome check to the if condition at line 2762.
I had tested this functionality myself on all these browsers and they work as intended in both desktop and mobile versions.
Update: Added PDFJSDev checks to ensure no unnecessary code ends up in
the built-in Firefox PDF Viewer
89a1615cd1