Remove support for the old Span classes from source_maps.

pkg/source_maps/test/printer_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test.printer_test;
 
 import 'dart:convert';
 import 'package:unittest/unittest.dart';
-import 'package:source_maps/printer.dart';
-import 'package:source_maps/span.dart';
+import 'package:source_maps/source_maps.dart';
+import 'package:source_span/source_span.dart';
 import 'common.dart';
 
 main() {
   test('printer', () {
     var printer = new Printer('output.dart');
     printer..add('var ')
            ..mark(inputVar1)
            ..add('x = 3;\n')
            ..mark(inputFunction)
            ..add('f(')
@@ skipping 25 matching lines @@
         ..mark(inputExpr)
         ..add('_s')
         ..add(segments[4], projectMarks: true)
         ..add('_s')
         ..add(segments[5], projectMarks: true);
 
     expect(printer.text, out);
     // 8 new lines in the source map:
     expect(printer.map.split(';').length, 8);
 
-    asFixed(Span s) => new FixedSpan(s.sourceUrl,
-        s.start.offset, s.start.line, s.start.column,
-        text: s.text, isIdentifier: s.isIdentifier);
+    asFixed(SourceMapSpan s) => new SourceMapSpan(s.start, s.end, s.text,
+        isIdentifier: s.isIdentifier);
 
     // The result is the same if we use fixed positions
     var printer2 = new Printer('output2.dart');
-    printer2..mark(new FixedSpan('input.dart', 0, 0, 0))
+    printer2..mark(new SourceLocation(0, sourceUrl: 'input.dart').pointSpan())
         ..add(segments[0], projectMarks: true)
         ..mark(asFixed(inputVar1))
         ..add('_s')
         ..add(segments[1], projectMarks: true)
         ..mark(asFixed(inputFunction))
         ..add('_s')
         ..add(segments[2], projectMarks: true)
         ..mark(asFixed(inputVar2))
         ..add('_s')
         ..add(segments[3], projectMarks: true)
@@ skipping 40 matching lines @@
       for (int i = 0; i < lines.length; i++) {
         if (i == 5) printer.indent++;
         printer.addLine(lines[i].replaceAll('long', '_s').trim());
         if (i == 5) printer.indent--;
       }
       printer.build('output.dart');
       expect(printer.text, out);
     });
   });
 }