Set 'enclosingElement' for FunctionElementImpl_forLUB.

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

Index: pkg/analyzer/lib/src/summary/resynthesize.dart
diff --git a/pkg/analyzer/lib/src/summary/resynthesize.dart b/pkg/analyzer/lib/src/summary/resynthesize.dart
index b3f32cda59e956432f621e97ecfe8babf2e68a28..cce2691bcaf2d3af01f4b6e63aada14174239545 100644
--- a/pkg/analyzer/lib/src/summary/resynthesize.dart
+++ b/pkg/analyzer/lib/src/summary/resynthesize.dart
@@ -1688,8 +1688,8 @@ class _UnitResynthesizer {
           new GenericFunctionTypeElementImpl.forSerialized(context, type);
       return element.type;
     } else if (type.syntheticReturnType != null) {
-      FunctionElementImpl element = new FunctionElementImpl_forLUB(
-          unit, context.typeParameterContext, type);
+      FunctionElementImpl element =
+          new FunctionElementImpl_forLUB(context, type);
       return element.type;
     } else {
       DartType getTypeArgument(int i) {