How can I inject into a Safari Web Content process?

[GoogleCodeExporter]

I would like to disable horizontal elastic scroll because it is the reason for 
jerky scrolling in Safari, scrolling even just slightly into the horizontal 
elastic area when doing a vertical trackpad scroll (with inertia) cancels the 
scroll and the page jumps back to its pre-scroll position.

The issue with loading I'm having is that com.apple.WebProcess doesn't send the 
app launch notification and in my attempt to inject manually the Apple script 
below errors with error type -10810:

tell application id "com.apple.WebProcess"
    inject SIMBL into Snow Leopard
end tell

Original issue reported on code.google.com by indieki...@gmail.com on 24 Dec 2013 at 7:39