Span.getLocationMessage returns incorrect output for lines without trailing newlines

[nex3]

If a span points to the final line in a file, and that line doesn't end in a newline, the arrows in getLocationMessage will be rendered on the same line as the source text. For example:

    Error on line 12, column 28 of pubspec.yaml: Error loading transformer: I hate these settings!
      - app/src/html_rewriter: {} ^^

[DartBot]

This issue has been moved to dart-lang/tools#1593.