Preserve isConst when cloning.

pkg/kernel/lib/clone.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 library kernel.clone;
 
 import 'ast.dart';
 import 'type_algebra.dart';
 
 /// Visitor that return a clone of a tree, maintaining references to cloned
 /// objects.
@@ skipping 101 matching lines @@
     return new DirectMethodInvocation(
         clone(node.receiver), node.target, clone(node.arguments));
   }
 
   visitSuperMethodInvocation(SuperMethodInvocation node) {
     return new SuperMethodInvocation(
         node.name, clone(node.arguments), node.interfaceTarget);
   }
 
   visitStaticInvocation(StaticInvocation node) {
-    return new StaticInvocation(node.target, clone(node.arguments));
+    return new StaticInvocation(node.target, clone(node.arguments),
+        isConst: node.isConst);
   }
 
   visitConstructorInvocation(ConstructorInvocation node) {
-    return new ConstructorInvocation(node.target, clone(node.arguments));
+    return new ConstructorInvocation(node.target, clone(node.arguments),
+        isConst: node.isConst);
   }
 
   visitNot(Not node) {
     return new Not(clone(node.operand));
   }
 
   visitLogicalExpression(LogicalExpression node) {
     return new LogicalExpression(
         clone(node.left), node.operator, clone(node.right));
   }
@@ skipping 255 matching lines @@
   visitArguments(Arguments node) {
     return new Arguments(node.positional.map(clone).toList(),
         types: node.types.map(visitType).toList(),
         named: node.named.map(clone).toList());
   }
 
   visitNamedExpression(NamedExpression node) {
     return new NamedExpression(node.name, clone(node.value));
   }
 }