Refactor Source.

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 68af3caf11575811747e83983454b28249e02c0f..a4cba8f776f7e254a34741bb398ec02ad0219893 100644
--- a/sdk/lib/_internal/pub/lib/src/lock_file.dart
+++ b/sdk/lib/_internal/pub/lib/src/lock_file.dart
@@ -60,12 +60,10 @@ class LockFile {
         }
         var description = spec['description'];
 
-        // Parse the description if we know the source.
-        if (sources.contains(sourceName)) {
-          var source = sources[sourceName];
-          description = source.parseDescription(filePath, description,
-              fromLockFile: true);
-        }
+        // Let the source parse the description.
+        var source = sources[sourceName];
+        description = source.parseDescription(filePath, description,
+            fromLockFile: true);
 
         var id = new PackageId(name, sourceName, version, description);