Check for one-to-many source mappings.

tests/compiler/dart2js/sourcemaps/source_mapping_test_viewer.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.
 
 /// Visualization of source mappings generated and tested in
 /// 'source_mapping_test.dart'.
 
 library source_mapping.test.viewer;
 
 import 'dart:async';
@@ skipping 115 matching lines @@
 
 Future<Measurement> runTest(
     String config,
     String filename,
     List<String> options,
     {Uri outputUri,
      bool verbose}) async {
   TestResult result =
       await runTests(config, filename, options, verbose: verbose);
   if (outputUri != null) {
-    if (result.failureMap.isNotEmpty) {
-      result.failureMap.forEach((info, missingCodePoints) {
-        print("Missing code points for ${info.element} in '$filename' "
-              "in config '$config':");
-        for (CodePoint codePoint in missingCodePoints) {
-          print("  $codePoint");
-        }
-      });
+    if (result.missingCodePointsMap.isNotEmpty) {
+      result.printMissingCodePoints();
+    }
+    if (result.multipleNodesMap.isNotEmpty) {
+      result.printMultipleNodes();
+    }
+    if (result.multipleOffsetsMap.isNotEmpty) {
+      result.printMultipleOffsets();
     }
     createTraceSourceMapHtml(outputUri, result.processor, result.userInfoList);
   }
   return new Measurement(config, filename,
-      result.failureMap.values.fold(0, (s, i) => s + i.length),
+      result.missingCodePointsMap.values.fold(0, (s, i) => s + i.length),
       result.userInfoList.fold(0, (s, i) => s + i.codePoints.length));
 }
 
 class Measurement {
   final String config;
   final String filename;
 
   final int missing;
   final int count;
 
   Measurement(this.config, this.filename, this.missing, this.count);
 
   String toString() {
     double percentage = 100 * missing / count;
     return "Config '${config}', file: '${filename}': "
            "$missing of $count ($percentage%) missing";
   }
 }