dart2js cps: Handle optional parameters in builder.

pkg/analyzer2dart/lib/src/cps_generator.dart

Index: pkg/analyzer2dart/lib/src/cps_generator.dart
diff --git a/pkg/analyzer2dart/lib/src/cps_generator.dart b/pkg/analyzer2dart/lib/src/cps_generator.dart
index 7a4499ac9434b2753abecc7fc76a2d4b8fe2fb8c..a2dc9e677271b78fe81a0469a625146d5c77c1c2 100644
--- a/pkg/analyzer2dart/lib/src/cps_generator.dart
+++ b/pkg/analyzer2dart/lib/src/cps_generator.dart
@@ -217,9 +217,10 @@ class CpsGeneratingVisitor extends SemanticVisitor<ir.Node>
                                      AccessSemantics semantics) {
     analyzer.Element staticElement = semantics.element;
     dart2js.Element element = converter.convertElement(staticElement);
+    ir.Primitive receiver = irBuilder.buildLocalGet(element);
     List<ir.Definition> arguments = visitArguments(node.argumentList);
-    return irBuilder.buildLocalInvocation(
-      element,
+    return irBuilder.buildFunctionExpressionInvocation(
+      receiver,
       createSelectorFromMethodInvocation(
           node.argumentList, node.methodName.name),
       arguments);