Clean up the semantics of package descriptions.

lib/src/pubspec.dart

Index: lib/src/pubspec.dart
diff --git a/lib/src/pubspec.dart b/lib/src/pubspec.dart
index e53a252b2fc700c710a1100830b80eed40226ffb..db55b4d5a41be5c1edfc6d0ad22b8ddc288a2466 100644
--- a/lib/src/pubspec.dart
+++ b/lib/src/pubspec.dart
@@ -496,19 +496,17 @@ class Pubspec {
       }
 
       // Let the source validate the description.
-      var description = _wrapFormatException('description',
-          descriptionNode.span, () {
+      var ref = _wrapFormatException('description', descriptionNode.span, () {
         var pubspecPath;
         if (_location != null && _isFileUri(_location)) {
           pubspecPath = path.fromUri(_location);
         }
 
-        return _sources[sourceName].parseDescription(
-            pubspecPath, descriptionNode.value, fromLockFile: false);
+        return _sources[sourceName].parseRef(name, descriptionNode.value,
+            containingPath: pubspecPath);
       });
 
-      dependencies.add(new PackageDep(
-          name, sourceName, versionConstraint, description));
+      dependencies.add(ref.withConstraint(versionConstraint));
     });
 
     return dependencies;