Fix shift in source map positions.

tests/compiler/dart2js/line_column_provider_test.dart

+// Copyright (c) 2015, 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.
+
+// Unittest for the [LineColumnCollector].
+
+import 'package:expect/expect.dart';
+import 'package:compiler/src/io/code_output.dart';
+import 'package:compiler/src/io/line_column_provider.dart';
+
+import 'output_collector.dart';
+
+test(List events, Map<int, List<int>> expectedPositions) {
+  BufferedEventSink sink = new BufferedEventSink();
+  LineColumnProvider lineColumnProvider = new LineColumnCollector();
+  CodeOutput output = new StreamCodeOutput(sink, [lineColumnProvider]);
+  for (var event in events) {
+    if (event is String) {
+      output.add(event);
+    } else if (event is CodeBuffer) {
+      output.addBuffer(event);
+    }
+  }
+  output.close();
+
+  expectedPositions.forEach((int offset, List<int> expectedPosition) {
+    if (expectedPosition == null) {
+      Expect.throws(() => lineColumnProvider.getLine(offset),
+                    (e) => true,
+                    'Expected out-of-bounds offset: $offset\n'
+                    'text:"""${sink.text}"""\n'
+                    'lineColumnProvider:$lineColumnProvider');
+    } else {
+      int line = lineColumnProvider.getLine(offset);
+      int column = lineColumnProvider.getColumn(line, offset);
+      Expect.equals(expectedPosition[0], line,
+          'Unexpected result: $offset -> $expectedPosition = [$line,$column]\n'
+          'text:"""${sink.text}"""\n'
+          'lineColumnProvider:$lineColumnProvider');
+      Expect.equals(expectedPosition[1], column,
+          'Unexpected result: $offset -> $expectedPosition = [$line,$column]\n'
+          'text:"""${sink.text}"""\n'
+          'lineColumnProvider:$lineColumnProvider');
+    }
+  });
+}
+
+main() {
+  test([""], {0: [0, 0], 1: null});
+
+  test([" "], {0: [0, 0], 1: [0, 1], 2: null});
+
+  test(["\n "], {0: [0, 0], 1: [1, 0], 2: [1, 1], 3: null});
+
+  Map positions = {0: [0, 0],
+                   1: [0, 1],
+                   2: [1, 0],
+                   3: [1, 1],
+                   4: [2, 0],
+                   5: [2, 1],
+                   6: null};
+
+  test(["a\nb\nc"], positions);
+
+  test(["a", "\nb\nc"], positions);
+
+  test(["a", "\n", "b\nc"], positions);
+
+  CodeBuffer buffer1 = new CodeBuffer();
+  buffer1.add("a\nb\nc");
+  test([buffer1], positions);
+
+  CodeBuffer buffer2 = new CodeBuffer();
+  buffer2.add("\nb\nc");
+  test(["a", buffer2], positions);
+
+  CodeBuffer buffer3 = new CodeBuffer();
+  buffer3.add("a");
+  test([buffer3, buffer2], positions);
+
+  CodeBuffer buffer4 = new CodeBuffer();
+  buffer4.addBuffer(buffer3);
+  test([buffer4, buffer2], positions);
+}