Add test for expected source mappings

tests/compiler/dart2js/sourcemaps/stacktrace_test.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/compiler_new.dart';
@@ skipping 191 matching lines @@
 ];
 
 class Test {
   final String code;
   final List<StackTraceLine> expectedLines;
   final List<StackTraceLine> unexpectedLines;
 
   Test(this.code, this.expectedLines, this.unexpectedLines);
 }
 
-const int _LF = 0x0A;
-const int _CR = 0x0D;
-const int _LBRACE = 0x7B;
-
 Test processTestCode(String code) {
   Map<int, StackTraceLine> stackTraceMap = <int, StackTraceLine>{};
   List<StackTraceLine> unexpectedLines = <StackTraceLine>[];
-  AnnotatedCode annotatedCode = new AnnotatedCode(code);
+  AnnotatedCode annotatedCode = new AnnotatedCode.fromText(code);
   for (Annotation annotation in annotatedCode.annotations) {
     int colonIndex = annotation.text.indexOf(':');
     String indexText = annotation.text.substring(0, colonIndex);
     String methodName = annotation.text.substring(colonIndex + 1);
     StackTraceLine stackTraceLine = new StackTraceLine(
         methodName, INPUT_FILE_NAME, annotation.lineNo, annotation.columnNo);
     if (indexText == '') {
       unexpectedLines.add(stackTraceLine);
     } else {
       int stackTraceIndex = int.parse(indexText);
@@ skipping 324 matching lines @@
   const LineException(
       '_awaitOnObject.<anonymous function>', 'async_patch.dart'),
   const LineException('_RootZone.runUnary', 'zone.dart'),
   const LineException('_FutureListener.handleValue', 'future_impl.dart'),
   const LineException(
       '_Future._propagateToListeners.handleValueCallback', 'future_impl.dart'),
   const LineException('_Future._propagateToListeners', 'future_impl.dart'),
   const LineException(
       '_Future._addListener.<anonymous function>', 'future_impl.dart'),
 ];