dart2js cps: Add a pass for eliminating bounds checks.

tests/compiler/dart2js/js_backend_cps_ir_operators_test.dart

Index: tests/compiler/dart2js/js_backend_cps_ir_operators_test.dart
diff --git a/tests/compiler/dart2js/js_backend_cps_ir_operators_test.dart b/tests/compiler/dart2js/js_backend_cps_ir_operators_test.dart
index 877b3714f376f5d65d815b282a1144b04a5ee2f2..a6d7a1cbf091a67afb8e025ff0bb0a19e82fcce7 100644
--- a/tests/compiler/dart2js/js_backend_cps_ir_operators_test.dart
+++ b/tests/compiler/dart2js/js_backend_cps_ir_operators_test.dart
@@ -84,10 +84,8 @@ main() {
   print(list);
 }""", r"""
 function() {
-  var list = [1, 2, 3], v0 = 1;
-  if (v0 < 0 || v0 >= list.length)
-    H.ioore(list, v0);
-  list[v0] = 6;
+  var list = [1, 2, 3];
+  list[1] = 6;
   P.print(list);
 }"""),
 ];