dart2js cps: Combine integer type check with bounds check.

tests/compiler/dart2js/cps_ir/expected/optimize_indexers.js

 // Expectation for test: 
 // // Method to test: function(test)
 // import 'package:expect/expect.dart';
 // 
 // // This example illustrates a case we wish to do better in terms of inlining and
 // // code generation.
 // //
 // // Naively this function would be compiled without inlining Wrapper.[],
 // // JSArray.[] and Wrapper.[]= because:
 // // JSArray.[] is too big (14 nodes)
@@ skipping 18 matching lines @@
 // class Wrapper {
 //   final List arr = <bool>[true, false, false, true];
 //   operator[](int i) => this.arr[i];
 //   operator[]=(int i, v) {
 //     if (i > arr.length - 1) arr.length = i + 1;
 //     return arr[i] = v;
 //   }
 // }
 
 function(data, x) {
-  var v0 = J.$add$ns(x, 1), v1 = data.arr, v2 = v1.length;
-  if (typeof x !== "number" || Math.floor(x) !== x)
-    return H.iae(x);
-  if (x < 0 || x >= v2)
+  var v0 = J.$add$ns(x, 1), v1 = data.arr;
+  if (x >>> 0 !== x || x >= v1.length)
     return H.ioore(v1, x);
   data.$indexSet(0, v0, v1[x]);
 }