How did you manage with the web inspector? There's no built-in web inspector on any mainstream mobile browser that I'm aware of and the only way to do it would be to use firebug.js like the good old days.
I toyed with it briefly, the performance is about what I expected given the hardware I was using. Which is to say, not a terrible amount of overhead
https://github.com/laem/chromium
It takes such a long time to compile chromium that this wasn't a good solution in the long term, but worked perfectly.
Don't remember how I did then, long term. But yes, this was one of the major hurdles.
devtools is just a set of html and javascript after all, and talks to the page its debugging via a websocket with special powers.
But it's a heavy task in the long run.