Elements. Print SetterElement variable.

Change-Id: I829495baba82bc481639185eb3e91a42ffeaaf77
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442342
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>

Author: scheglov

pkg/analyzer/test/src/summary/element_text.dart

@@ -1518,6 +1518,7 @@ class _Element2Writer extends _AbstractElementWriter {
         _writeFormalParameterElement,
       );
       _writeReturnType(e.returnType);
+      _writeElementReference('variable', e.variable);
       // _writeNonSyntheticElement(e);
       // writeLinking();
     });