Use closure conversion in new dart2js backend.

pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart

 // Copyright (c) 2014, 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.
 
 part of tree_ir.optimization;
 
 /**
  * Performs the following transformations on the tree:
  * - Assignment propagation
  * - If-to-conditional conversion
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     // the expression statement.  If they can occur here they should be
     // handled well.
     List<Assign> savedEnvironment = environment;
     environment = <Assign>[];
     node.next = visitStatement(node.next);
     assert(environment.isEmpty);
     environment = savedEnvironment;
     return node;
   }
 
+  Statement visitSetField(SetField node) {
+    node.next = visitStatement(node.next);
+    node.object = visitExpression(node.object);
+    node.value = visitExpression(node.value);
+    return node;
+  }
+
+  Expression visitGetField(GetField node) {
+    node.object = visitExpression(node.object);
+    return node;
+  }
+
+  Expression visitCreateBox(CreateBox node) {
+    return node;
+  }
+
+  Expression visitCreateClosureClass(CreateClosureClass node) {
+    for (int i = node.arguments.length - 1; i >= 0; --i) {
+      node.arguments[i] = visitExpression(node.arguments[i]);
+    }
+    return node;
+  }
+
   /// If [s] and [t] are similar statements we extract their subexpressions
   /// and returns a new statement of the same type using expressions combined
   /// with the [combine] callback. For example:
   ///
   ///   combineStatements(Return E1, Return E2) = Return combine(E1, E2)
   ///
   /// If [combine] returns E1 then the unified statement is equivalent to [s],
   /// and if [combine] returns E2 the unified statement is equivalence to [t].
   ///
   /// It is guaranteed that no side effects occur between the beginning of the
@@ skipping 146 matching lines @@
   }
 
   Expression makeCondition(Expression e, bool polarity) {
     return polarity ? e : new Not(e);
   }
 
   Statement getBranch(If node, bool polarity) {
     return polarity ? node.thenStatement : node.elseStatement;
   }
 }