Clean up the semantics of package descriptions.

test/pubspec_test.dart

Index: test/pubspec_test.dart
diff --git a/test/pubspec_test.dart b/test/pubspec_test.dart
index 54be75b00828d696fecb537278380d6c4942f71b..d662fae119e19923e112723fa516a32c0dbaf77a 100644
--- a/test/pubspec_test.dart
+++ b/test/pubspec_test.dart
@@ -19,6 +19,9 @@ import 'test_pub.dart';
 class MockSource extends Source {
   final String name = "mock";
 
+  Future<List<PackageId>> doGetVersions(PackageRef ref) =>
+      throw new UnsupportedError("Cannot get mock package versions.");
+
   Future<Pubspec> doDescribe(PackageId id) => throw new UnsupportedError(
       "Cannot describe mock packages.");
 
@@ -28,12 +31,14 @@ class MockSource extends Source {
   String getDirectory(PackageId id) => throw new UnsupportedError(
       "Cannot get the directory for mock packages.");
 
-  dynamic parseDescription(String filePath, description,
-                           {bool fromLockFile: false}) {
+  PackageRef parseRef(String name, description, {String containingPath}) {
     if (description != 'ok') throw new FormatException('Bad');
-    return description;
+    return new PackageRef(name, this.name, description);
   }
 
+  PackageId parseId(String name, Version version, description) =>
+      new PackageId(name, this.name, version, description);
+
   bool descriptionsEqual(description1, description2) =>
       description1 == description2;