Include default values for default field formal parameters into text dump.

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

Index: pkg/analyzer/test/src/summary/element_text.dart
diff --git a/pkg/analyzer/test/src/summary/element_text.dart b/pkg/analyzer/test/src/summary/element_text.dart
index 65d7c8064161bfe5b6039e38ab40e35e10829025..6a87687760a38e5239a85d996203b152309f96d9 100644
--- a/pkg/analyzer/test/src/summary/element_text.dart
+++ b/pkg/analyzer/test/src/summary/element_text.dart
@@ -588,8 +588,9 @@ class _ElementWriter {
 
   void writeParameterElement(ParameterElement e) {
     String defaultValueSeparator;
-    Expression defaultValue =
-        e is DefaultParameterElementImpl ? e.constantInitializer : null;
+    Expression defaultValue = e is ConstVariableElement
+        ? (e as ConstVariableElement).constantInitializer
+        : null;
     String closeString;
     ParameterKind kind = e.parameterKind;
     if (kind == ParameterKind.REQUIRED) {