UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36

Steps to reproduce the problem:
I would like you to consider implementing such warning. It would help people who forget to enable the feature and then wonder what went wrong.

Requested here for example:
https://github.com/binaryage/cljs-devtools/issues/16

What is the expected behavior?

What went wrong?
People's confusion is greater than necessary :)

Did this work before? N/A 

Chrome version: 53.0.2763.0  Channel: canary
OS Version: OS X 10.11.6
Flash Version: Shockwave Flash 21.0 r0

Actually I was able to implement it but using some terrible hacks.

I rely on the fact that I print info line into console showing cljs-devtools version anyways. There I add "invisible" printing of a function object.  This way I can detect when console gets opened and that line get rendered regardless of CF support / enabled state (DevTools use .toString() to print function objects, so I override it in my custom case).

I also implement a special no-op CF which I use to detect if custom formatters were enabled after console was opened. I also have to fight the fact that CFs are applied asynchronously.