Make sure we're not trying to optimize an int check if the input can be a number.

tests/compiler/dart2js/concrete_type_inference_test.dart

Index: tests/compiler/dart2js/concrete_type_inference_test.dart
===================================================================
--- tests/compiler/dart2js/concrete_type_inference_test.dart	(revision 27024)
+++ tests/compiler/dart2js/concrete_type_inference_test.dart	(working copy)
@@ -54,7 +54,7 @@
     var inferrer = compiler.typesTask.typesInferrer;
     Expect.identical(compiler.typesTask.boolType, type);
   });
-  checkPrintType('1.0', (compiler, type) {
+  checkPrintType('1.5', (compiler, type) {
     var inferrer = compiler.typesTask.typesInferrer;
     Expect.identical(compiler.typesTask.doubleType, type);
   });