Remove redundancy in source map entries.

tests/compiler/dart2js/source_map_validator_helper.dart

+// Copyright (c) 2014, 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:io';
+import 'dart:convert';
+import 'dart:async';
+
+import 'package:path/path.dart' as path;
+import 'package:expect/expect.dart';
+import 'package:source_maps/source_maps.dart';
+
+validateSourceMap(Uri targetUri) {
+  Uri mapUri = getMapUri(targetUri);
+  SingleMapping sourceMap = getSourceMap(mapUri);
+  checkFileReferences(targetUri, mapUri, sourceMap);
+  checkRedundancy(sourceMap);
+}
+
+checkFileReferences(Uri targetUri, Uri mapUri, SingleMapping sourceMap) {
+  Expect.equals(targetUri, mapUri.resolve(sourceMap.targetUrl));
+  print('Checking sources');
+  sourceMap.urls.forEach((String url) {
+    Expect.isTrue(new File.fromUri(mapUri.resolve(url)).existsSync());
+  });
+}
+
+checkRedundancy(SingleMapping sourceMap) {
+  sourceMap.lines.forEach((TargetLineEntry line) {
+    TargetEntry previous = null;
+    for (TargetEntry next in line.entries) {
+      if (previous != null) {
+        Expect.isFalse(sameSourcePoint(previous, next),
+            '$previous and $next are consecutive entries on line $line in the '
+            'source map but point to same source locations');
+      }
+      previous = next;
+    }
+  });
+}
+
+sameSourcePoint(TargetEntry entry, TargetEntry otherEntry) {
+  return
+      (entry.sourceUrlId == otherEntry.sourceUrlId) &&
+      (entry.sourceLine == otherEntry.sourceLine) &&
+      (entry.sourceColumn == otherEntry.sourceColumn) &&
+      (entry.sourceNameId == otherEntry.sourceNameId);
+}
+
+Uri getMapUri(Uri targetUri) {
+  print('Accessing $targetUri');
+  File targetFile = new File.fromUri(targetUri);
+  Expect.isTrue(targetFile.existsSync());
+  List<String> target = targetFile.readAsStringSync().split('\n');
+  String mapReference = target[target.length - 3]; // #sourceMappingURL=<url>
+  Expect.isTrue(mapReference.startsWith('//# sourceMappingURL='));
+  String mapName = mapReference.substring(mapReference.indexOf('=') + 1);
+  return targetUri.resolve(mapName);
+}
+
+SingleMapping getSourceMap(Uri mapUri) {
+  print('Accessing $mapUri');
+  File mapFile = new File.fromUri(mapUri);
+  Expect.isTrue(mapFile.existsSync());
+  return new SingleMapping.fromJson(
+      JSON.decode(mapFile.readAsStringSync()));
+}
+
+copyDirectory(Directory sourceDir, Directory destinationDir) {
+  sourceDir.listSync().forEach((FileSystemEntity element) {
+    String newPath = path.join(destinationDir.path,
+                               path.basename(element.path));
+    if (element is File) {
+      element.copySync(newPath);
+    } else if (element is Directory) {
+      Directory newDestinationDir = new Directory(newPath);
+      newDestinationDir.createSync();
+      copyDirectory(element, newDestinationDir);
+    }
+  });
+}
+
+Future<Directory> createTempDir() {
+  return Directory.systemTemp
+      .createTemp('sourceMap_test-')
+      .then((Directory dir) {
+    return dir;
+  });
+}