dart2js cps: More aggressive operator specialization.

tests/compiler/dart2js/cps_ir/expected/argument_refinement_19.js

 // Expectation for test: 
 // main() {
 //   var x = int.parse('1233');
 //   var y = int.parse('1234');
 //   print(x / 2);
 //   print(x is num);
 //   print(y is num);
 //   print(x + y);
 //   print(y is num);
 // }
 
 function() {
-  var x = P.int_parse("1233", null, null), y = P.int_parse("1234", null, null), v0 = typeof y === "number";
-  P.print(J.$div$n(x, 2));
+  var x = P.int_parse("1233", null, null), y = P.int_parse("1234", null, null);
+  P.print(x / 2);
   P.print(true);
-  P.print(v0);
-  if (!v0)
-    throw H.wrapException(H.argumentErrorValue(y));
+  P.print(typeof y === "number");
+  if (typeof y !== "number")
+    return H.iae(y);
   P.print(x + y);
   P.print(true);
 }