Support for NamedExpression(s) as constructor initializer arguments.

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

Index: pkg/analyzer/lib/src/summary/summarize_const_expr.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_const_expr.dart b/pkg/analyzer/lib/src/summary/summarize_const_expr.dart
index 17a0b511e4706479aa5fc89fa322b99f3887e4d8..f76fed2ec7af5546ff1d28960e9054a36e89b07b 100644
--- a/pkg/analyzer/lib/src/summary/summarize_const_expr.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_const_expr.dart
@@ -45,11 +45,16 @@ UnlinkedConstructorInitializer serializeConstructorInitializer(
  */
 abstract class AbstractConstExprSerializer {
   /**
-   * See [UnlinkedConstBuilder.isInvalid].
+   * See [UnlinkedConstBuilder.isValidConst].
    */
   bool isValidConst = true;
 
   /**
+   * See [UnlinkedConstBuilder.nmae].
+   */
+  String name = null;
+
+  /**
    * See [UnlinkedConstBuilder.operations].
    */
   final List<UnlinkedConstOperation> operations = <UnlinkedConstOperation>[];
@@ -91,6 +96,11 @@ abstract class AbstractConstExprSerializer {
    */
   void serialize(Expression expr) {
     try {
+      if (expr is NamedExpression) {
+        NamedExpression namedExpression = expr;
+        name = namedExpression.name.label.name;
+        expr = namedExpression.expression;
+      }
       _serialize(expr);
     } on StateError {
       isValidConst = false;
@@ -152,6 +162,7 @@ abstract class AbstractConstExprSerializer {
   UnlinkedConstBuilder toBuilder() {
     return new UnlinkedConstBuilder(
         isValidConst: isValidConst,
+        name: name,
         operations: operations,
         assignmentOperators: assignmentOperators,
         ints: ints,