Fairly straightforward - this patch adds instrumentation into the profiling
RAII helper which is inserted into all WebIDL calls in order to include them
when running with JS Execution Tracing enabled.
Locally times on the attribute.specified getter microbenchmark were at ~5.6ns
without this patch and ~5.9 with the patch. Assuming that is real, is that an
acceptable perf hit here? The feature seems to be quite useful.
Differential Revision: https://phabricator.services.mozilla.com/D221690
