dart2js cps: Compile some loops as 'for' loops.

tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart

Index: tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart
diff --git a/tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart b/tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart
index 4e7b0cfdcdd8abf19ae8225e9395cce55a7a01e9..bb5e9020ab0b68387ee48a7408bb873701685809 100644
--- a/tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart
+++ b/tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart
@@ -34,17 +34,12 @@ main() {
 r"""
 function() {
   var l = ["hest", ["h", "e", "s", "t"]], i = 0, x_, x, j;
-  P.print(l.length);
-  while (i < l.length) {
+  for (P.print(l.length); i < l.length; i = i + 1) {
     if (i < 0 || i >= l.length)
       H.ioore(l, i);
     x_ = J.getInterceptor$as(x = l[i]);
-    j = 0;
-    while (j < x_.get$length(x)) {
+    for (j = 0; j < x_.get$length(x); j = j + 1)
       P.print(x_.$index(x, j));
-      j = j + 1;
-    }
-    i = i + 1;
   }
 }"""),
 ];