dart2js cps: Add a pass for eliminating bounds checks.

pkg/compiler/lib/src/cps_ir/shrinking_reductions.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 dart2js.cps_ir.shrinking_reductions;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
 
 /**
@@ skipping 474 matching lines @@
         } else if (_isBetaContLin(cont)) {
           worklist.add(new _ReductionTask(_ReductionKind.BETA_CONT_LIN, cont));
         }
       }
     }
   }
 }
 
 /// Traverses the CPS term and sets node.parent for each visited node.
 class ParentVisitor extends RecursiveVisitor {
+  static final ParentVisitor _instance = new ParentVisitor();
+  static void setParentPointers(Node node) => _instance.visit(node);
+
   processFunctionDefinition(FunctionDefinition node) {
     node.body.parent = node;
     if (node.thisParameter != null) node.thisParameter.parent = node;
     int index = 0;
     node.parameters.forEach((Definition parameter) {
       parameter.parent = node;
       if (parameter is Parameter) parameter.parentIndex = index++;
     });
     node.returnContinuation.parent = node;
     node.body.parent = node;
@@ skipping 231 matching lines @@
   }
 
   String toString() => "$kind: $node";
 }
 
 /// A dummy class used solely to mark nodes as deleted once they are removed
 /// from a term.
 class _DeletedNode extends Node {
   accept(_) => null;
 }