dart2js cps: Direct access on JS arrays.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.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.
 
 library tree_ir_builder;
 
 import '../dart2jslib.dart' as dart2js;
 import '../elements/elements.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
 import '../util/util.dart' show CURRENT_ELEMENT_SPANNABLE;
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     } else {
       assert(node.continuation == null);
       return new ForeignStatement(
           node.codeTemplate,
           node.type,
           node.arguments.map(getVariableUse).toList(growable: false),
           node.nativeBehavior,
           node.dependency);
     }
   }
+
+  Expression visitGetLength(cps_ir.GetLength node) {
+    return new GetLength(getVariableUse(node.object));
+  }
+
+  Expression visitGetIndex(cps_ir.GetIndex node) {
+    return new GetIndex(getVariableUse(node.object),
+                        getVariableUse(node.index));
+  }
+
+  Expression visitSetIndex(cps_ir.SetIndex node) {
+    return new SetIndex(getVariableUse(node.object),
+                        getVariableUse(node.index),
+                        getVariableUse(node.value));
+  }
 }