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

sdk/lib/_internal/compiler/implementation/types/inferrer_visitor.dart

Index: sdk/lib/_internal/compiler/implementation/types/inferrer_visitor.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/types/inferrer_visitor.dart	(revision 27024)
+++ sdk/lib/_internal/compiler/implementation/types/inferrer_visitor.dart	(working copy)
@@ -611,7 +611,13 @@
   }
 
   T visitLiteralDouble(LiteralDouble node) {
-    return types.doubleType;
+    ConstantSystem constantSystem = compiler.backend.constantSystem;
+    Constant constant = constantSystem.createDouble(node.value);
+    // The JavaScript backend may turn this literal into an integer at
+    // runtime.
+    return constantSystem.isDouble(constant)
+        ? types.doubleType
+        : types.intType;
   }
 
   T visitLiteralInt(LiteralInt node) {