We currently have stack-walking code in JfrCPUTimeThreadSampler and JfrThreadSampler. Both implementations share some code, but have their own code paths in other places, and for no good reason. Those should be consolidated, in order to reduce mess, reduce maintenance work (e.g. bugs fixed - or improvements made - in one place, but not the other).

Also, there are a few other places that also walk stacks, e.g. the JVMTI family of GetStackTrace functions, and perhaps some more, which would also benefit from having a shared stack-walking facility. Last but not least, this could be used to provide an AsyncGetCallTrace replacement that actually works, and is safe, and Does The Right Thing.