Use indentation for maps in lockfile.

sdk/lib/_internal/pub/lib/src/lock_file.dart

Index: sdk/lib/_internal/pub/lib/src/lock_file.dart
diff --git a/sdk/lib/_internal/pub/lib/src/lock_file.dart b/sdk/lib/_internal/pub/lib/src/lock_file.dart
index 316e8b58803b9b72e6421b8804c8ac146849b79e..7f69ca1ce098ab41e509bc99f1eaeb3e8743d48c 100644
--- a/sdk/lib/_internal/pub/lib/src/lock_file.dart
+++ b/sdk/lib/_internal/pub/lib/src/lock_file.dart
@@ -4,12 +4,12 @@
 
 library lock_file;
 
-import 'dart:json' as json;
 import 'dart:collection';
 
 import 'package:yaml/yaml.dart';
 
 import 'io.dart';
+import 'log.dart' as log;
 import 'package.dart';
 import 'source_registry.dart';
 import 'utils.dart';
@@ -88,25 +88,20 @@ class LockFile {
 
   /// Returns the serialized YAML text of the lock file.
   String serialize() {
-    var packagesObj = new LinkedHashMap<String, Map>();
-
-    // Sort the packages by name.
-    var sortedKeys = packages.keys.toList();
-    sortedKeys.sort();
-    sortedKeys.forEach((name) {
-      packagesObj[name] = {
+    // Convert the dependencies to a simple object.
+    var data = {};
+    packages.forEach((name, package) {
+      data[name] = {
         'version': packages[name].version.toString(),
         'source': packages[name].source,
         'description': packages[name].description
       };
     });
 
-    // TODO(nweiz): Serialize using the YAML library once it supports
-    // serialization. For now, we use JSON, since it's a subset of YAML anyway.
-    return
-        '# Generated by pub\n'
-        '# See http://pub.dartlang.org/doc/glossary.html#lockfile\n'
-        '\n'
-        '${json.stringify({'packages': packagesObj})}\n';
+    return """
+# Generated by pub
+# See http://pub.dartlang.org/doc/glossary.html#lockfile
+${yamlToString({'packages': data})}
+""";
   }
 }