Merge kernel closure conversion into the Dart SDK

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 356 matching lines @@
         fileUri: node.fileUri);
   }
 
   visitTypeParameter(TypeParameter node) {
     var newNode = new TypeParameter(node.name);
     typeSubstitution[node] = new TypeParameterType(newNode);
     newNode.bound = visitType(node.bound);
     return newNode;
   }
 
+  TreeNode cloneFunctionNodeBody(FunctionNode node) => cloneOptional(node.body);
+
   visitFunctionNode(FunctionNode node) {
     var typeParameters = node.typeParameters.map(clone).toList();
     var positional = node.positionalParameters.map(clone).toList();
     var named = node.namedParameters.map(clone).toList();
-    return new FunctionNode(cloneOptional(node.body),
+    return new FunctionNode(cloneFunctionNodeBody(node),
         typeParameters: typeParameters,
         positionalParameters: positional,
         namedParameters: named,
         requiredParameterCount: node.requiredParameterCount,
         returnType: visitType(node.returnType),
         asyncMarker: node.asyncMarker);
   }
 
   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));
   }
 }