dart2js cps: Combine integer type check with bounds check.

pkg/compiler/lib/src/cps_ir/update_refinements.dart

 library dart2js.cps_ir.update_refinements;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart' show Pass;
 import 'type_mask_system.dart';
 import '../world.dart';
 
 /// Updates all references to use the most refined version in scope.
 ///
 /// [GVN] and [RedundantJoinElimination], and possibly other passes, can create
@@ skipping 55 matching lines @@
           node.refineType);
     }
     Primitive value = node.effectiveDefinition;
     Primitive old = refinementFor[value];
     refinementFor[value] = node;
     pushAction(() {
       refinementFor[value] = old;
     });
   }
 
+  visitBoundsCheck(BoundsCheck node) {
+    super.visitBoundsCheck(node);
+    if (node.hasIntegerCheck &&
+        typeSystem.isDefinitelyInt(node.index.definition.type)) {
+      node.checks &= ~BoundsCheck.INTEGER;
+    }
+  }
+
   processReference(Reference ref) {
     refine(ref);
   }
 
   bool refine(Reference ref) {
     Definition def = ref.definition;
     if (def is Primitive) {
       Primitive refinement = refinementFor[def.effectiveDefinition];
       if (refinement != null && refinement != ref.definition) {
         ref.changeTo(refinement);
         return true;
       }
     }
     return false;
   }
 }