Make pubspec.lock keep relative path if it is originally specified as relative in pubspec.yaml (iss…

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

 // Copyright (c) 2012, 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.
 
 library pub.source;
 
 import 'dart:async';
 
 import 'package:path/path.dart' as path;
 
@@ skipping 209 matching lines @@
   /// It should return if a (possibly modified) valid description, or throw a
   /// [FormatException] if not valid.
   ///
   /// [fromLockFile] is true when the description comes from a [LockFile], to
   /// allow the source to use lockfile-specific descriptions via [resolveId].
   dynamic parseDescription(String containingPath, description,
                            {bool fromLockFile: false}) {
     return description;
   }
 
+  /// When a [LockFile] is serialized, it uses this method to get the
+  /// [description] in the right format. [containingPath] references the
+  /// containing directory of the root package.
+  dynamic serializeDescription(String containingPath, description) {
+    return description;
+  }
+
   /// Returns whether or not [description1] describes the same package as
   /// [description2] for this source. This method should be light-weight. It
   /// doesn't need to validate that either package exists.
   ///
   /// By default, just uses regular equality.
   bool descriptionsEqual(description1, description2) =>
     description1 == description2;
 
   /// For some sources, [PackageId]s can point to different chunks of code at
   /// different times. This takes such an [id] and returns a future that
@@ skipping 18 matching lines @@
   /// Returns the [Package]s that have been downloaded to the system cache.
   List<Package> getCachedPackages() {
     if (shouldCache) {
       throw new UnimplementedError("Source $name must implement this.");
     }
   }
 
   /// Returns the source's name.
   String toString() => name;
 }