Fix bug in source-maps parsing: parser failed when most information could be

pkg/source_maps/test/common.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.
 
 /// Common input/output used by builder, parser and end2end tests
 library test.common;
 
 import 'package:source_maps/source_maps.dart';
 import 'package:unittest/unittest.dart';
 
 /// Content of the source file
 const String INPUT = '''
 /** this is a comment. */
 int longVar1 = 3;
 
 // this is a comment too
 int longName(int longVar2) {
   return longVar1 + longVar2;
 }
 ''';
 var input = new SourceFile.text('input.dart', INPUT);
 
 /// A span in the input file
 Span ispan(int start, int end, [bool isIdentifier = false]) =>
     new FileSpan(input, start, end, isIdentifier);
 
 Span inputVar1 = ispan(30, 38, true);
 Span inputFunction = ispan(74, 82, true);
 Span inputVar2 = ispan(87, 95, true);
+
+Span inputVar1NoSymbol = ispan(30, 38);
+Span inputFunctionNoSymbol = ispan(74, 82);
+Span inputVar2NoSymbol = ispan(87, 95);
+
 Span inputExpr = ispan(108, 127);
 
 /// Content of the target file
 const String OUTPUT = '''
 var x = 3;
 f(y) => x + y;
 ''';
 var output = new SourceFile.text('output.dart', OUTPUT);
 
 /// A span in the output file
 Span ospan(int start, int end, [bool isIdentifier = false]) =>
     new FileSpan(output, start, end, isIdentifier);
 
 Span outputVar1 = ospan(4, 5, true);
 Span outputFunction = ospan(11, 12, true);
 Span outputVar2 = ospan(13, 14, true);
+Span outputVar1NoSymbol = ospan(4, 5);
+Span outputFunctionNoSymbol = ospan(11, 12);
+Span outputVar2NoSymbol = ospan(13, 14);
 Span outputExpr = ospan(19, 24);
 
 /// Expected output mapping when recording the following four mappings:
 ///      inputVar1       <=   outputVar1
 ///      inputFunction   <=   outputFunction
 ///      inputVar2       <=   outputVar2
 ///      inputExpr       <=   outputExpr
 ///
 /// This mapping is stored in the tests so we can independently test the builder
 /// and parser algorithms without relying entirely on end2end tests.
@@ skipping 32 matching lines @@
     expect(span.end.line, inputSpan.end.line);
     expect(span.end.column, inputSpan.end.column);
     expect(span.end.offset, span.start.offset + inputSpan.text.length);
     if (realOffsets) expect(span.end.offset, inputSpan.end.offset);
   } else {
     expect(span.end.offset, span.start.offset);
     expect(span.end.line, span.start.line);
     expect(span.end.column, span.start.column);
   }
 }