Tracelogger
Tracelogger is a tool in the javascript engine that can pinpoint which engine in firefox is used. To create a log file you need to recompile the js shell with --enable-trace-logging. Afterwards every execution of a file will result in the creation of a /tmp/tracelogging.log file. This branch contains the python scripts to create a nice graph out of tracelogging files.
Tools V1
To create a tracelogging graph when you obtained the log file:
python generate.py [-h] [-w WIDTH] [-n NAME] [-r REVISION] logfile [logfile ...] -o outfile
e.g. python generate.py /tmp/tracelogging.log -o /tmp/test.html
The outfile should contain the graph. Put style.css and basic.js in the same folder and you should be good to go.
Tools V2
Experimental.