dart2js cps: Add a pass for eliminating bounds checks.

pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart

Index: pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
diff --git a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
index 0e617829efa8fe0dbd6082ebf985f30437f25934..2616c6794428f4ba3a2a4628576047acf14663e5 100644
--- a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
+++ b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
@@ -492,6 +492,9 @@ class _RemovalVisitor extends RecursiveVisitor {
 
 /// 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;