Reconsider StackFrame::getFileName and StackFrame::getLineNumber

StackFrame::getFileName and StackFrame::getLineNumber are originally proposed with the view of any stack walking code can migrate to the StackWalker API without the use of StackTraceElement.

File name and line number are useful for debugging and troubleshooting purpose. It has additional overhead to map from a method and BCI to look up the file name and line number.

StackFrame::toStackTraceElement method returns StackTraceElement that includes the file name and line number. There is no particular benefit to duplicate getFileName and getLineNumber methods in StackFrame. It is equivalently convenient to call StackFrame.toStackTraceElement().getFileName() (or getLineNumber).