Code review comment for lp:~lifeless/testresources/bug-284125

In the bug report, you suggest that "we could extend the protocol more deeply and say that we'll emite to the TestResult object being used, IFF it supports an additional function[s] for recording TestResources." I think I like that approach.

However, I think you're right when you suggest that we land this now and incorporate better ideas when we actually have them.

It seems that the docstring for 'trace_function' is out of date. It says "A callable that takes strings to output." However your patch currently calls it with operation, phase & resource manager. Please update the docstring before landing the patch.