This list is mostly dead these days, so you're better off asking on blink-dev.
However, mostly dead != completely dead, so ...
If you run run_web_tests.py with --debug-rwt-logging, it will dump stdout and stderr as it gets it. This gets very verbose if you're running multiple tests, but for a single test or a few tests, it's not too bad.
Apart from that, if you want to instrument things and just see the logs, log to stderr, not stdout. Trying to use run_web_tests + a debugger is a recipe for madness, but if you run wiht --debug-rwt-logging, you should see enough to tell you how to invoke content_shell directly on a test, and then and run *that* under gdb.
Hope this helps,
-- Dirk