Check syntax source to avoid "spurious" steps?

Here should:

        (define annotate-break?
          (let ([pos (syntax-position expr)]
                [src (syntax-source expr)])
            (and src pos

instead be:

        (define annotate-break?
          (let ([pos (syntax-position expr)]
                [src (syntax-source expr)])
            (and src pos
                 (equal? src (syntax-source stx))  ; <== NEW

In other words, check that the source is the same as that for the overall stx given to annotate-stx?

Otherwise, I'm seeing some odd results such as the first step for foo.rkt instead being in something like configure in module-begin from pre-base.rkt. That doesn't make much sense to a user, if a tool steps there. DrRacket doesn't step to the other file, it just does a step that doesn't go anywhere in the file actually being debugged; stepping again eventually reaches a step in the file and that aspect of the UI "comes alive".

Start at drracket/gui-debugger/annotator.rkt around line 232 and read how annotate-stx determines annotate-break?. Check the syntax source against the source for the overall stx, then verify that stepping in foo.rkt no longer produces a spurious step into pre-base.rkt or another source file.