Include default parameter values into summary.

pkg/analyzer/lib/src/summary/summarize_elements.dart

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index 8e041391e277cbf9bec0dd72b1991872095164f2..7b949c07b4bfe1f3894de67d9aeee2cb2d2cc3be 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -608,6 +608,13 @@ class _CompilationUnitSerializer {
         b.type = serializeTypeRef(type, context);
       }
     }
+    if (parameter is ConstVariableElement) {
+      ConstVariableElement constParameter = parameter as ConstVariableElement;
+      Expression initializer = constParameter.constantInitializer;
+      if (initializer != null) {
+        b.defaultValue = serializeConstExpr(initializer);
+      }
+    }
     return b;
   }