Hmm, does this make sense? I think you're including it for completeness. `\` is a valid path char on unix OSes, although probably never used. Perhaps, the semantics of `replacePathSeparator()` can be changed slightly, to essentially allow `'/'` paths - unix or web paths - to work on windows?

I think this change is ok as is, or just as 

    if (Platform.isWindows) {
      return path.replaceAll('/', Platform.pathSeparator);
    }

no strong feelings either way -