dart2js cps: Propagate container types for lists.

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 947d91956be1631098ee451412284a7c518e81ab..4de37b1545064385a848201dd1f3b7cffae4e2c6 100644
--- a/tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart
+++ b/tests/compiler/dart2js/js_backend_cps_ir_interceptors_test.dart
@@ -33,14 +33,11 @@ main() {
 }""",
 r"""
 function() {
-  var l = ["hest", ["h", "e", "s", "t"]], i = 0, x_, x, j;
-  for (P.print(l.length); i < l.length; i = i + 1) {
-    x_ = J.getInterceptor$as(x = l[i]);
-    for (j = 0; j < x_.get$length(x); j = j + 1) {
-      if (j >= x.length)
-        H.ioore(x, j);
+  var l = ["hest", ["h", "e", "s", "t"]], i = 0, x, j;
+  for (P.print(2); i < 2; i = i + 1) {
+    x = l[i];
+    for (j = 0; j < x.length; j = j + 1)
       P.print(x[j]);
-    }
   }
 }"""),
 ];