Compute covering offsets/lengths.

pkg/analysis_server/lib/src/services/refactoring/refactoring.dart

Index: pkg/analysis_server/lib/src/services/refactoring/refactoring.dart
diff --git a/pkg/analysis_server/lib/src/services/refactoring/refactoring.dart b/pkg/analysis_server/lib/src/services/refactoring/refactoring.dart
index a4d3c6b6a334daf1354de3ce8672994dbf3d78c3..baeab25627f2abe1e4cae456e196e6740d292f79 100644
--- a/pkg/analysis_server/lib/src/services/refactoring/refactoring.dart
+++ b/pkg/analysis_server/lib/src/services/refactoring/refactoring.dart
@@ -72,6 +72,18 @@ abstract class ExtractLocalRefactoring implements Refactoring {
   }
 
   /**
+   * The lengths of the expressions that cover the specified selection,
+   * from the down most to the up most.
+   */
+  List<int> get coveringExpressionLengths;
+
+  /**
+   * The offsets of the expressions that cover the specified selection,
+   * from the down most to the up most.
+   */
+  List<int> get coveringExpressionOffsets;
+
+  /**
    * True if all occurrences of the expression within the scope in which the
    * variable will be defined should be replaced by a reference to the local
    * variable. The expression used to initiate the refactoring will always be