Make the override warnings prettier.

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

Index: sdk/lib/_internal/pub/lib/src/source.dart
diff --git a/sdk/lib/_internal/pub/lib/src/source.dart b/sdk/lib/_internal/pub/lib/src/source.dart
index 676e1a6640913cddddacae0fda050926886078ed..a27a9095442cd9c116befc32d424f89bf9e8da35 100644
--- a/sdk/lib/_internal/pub/lib/src/source.dart
+++ b/sdk/lib/_internal/pub/lib/src/source.dart
@@ -228,12 +228,23 @@ abstract class Source {
   }
 
   /// 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.
+  /// [description] in the right format.
+  ///
+  /// [containingPath] is the containing directory of the root package.
   dynamic serializeDescription(String containingPath, description) {
     return description;
   }
 
+  /// When a package [description] is shown to the user, this is called to
+  /// convert it into a human-friendly form.
+  ///
+  /// By default, it just converts the description to a string, but sources
+  /// may customize this. [containingPath] is the containing directory of the
+  /// root package.
+  String formatDescription(String containingPath, description) {
+    return description.toString();
+  }
+
   /// 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.