dart2js cps: 'is' checks on types with type arguments.

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

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
index 6b78f6fffcf8e96d6d51e3e1766e41951f0ef459..c6033373ed6de7655de0ad1f4bcd30fbfa25b834 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
@@ -877,21 +877,17 @@ abstract class IrBuilderVisitor extends ast.Visitor<ir.Primitive>
       ast.Node expression,
       DartType type,
       _) {
-    ir.Primitive receiver = visit(expression);
-    return irBuilder.buildTypeOperator(
-        receiver, type,
-        isTypeTest: true,
-        isNotCheck: false);
+    ir.Primitive value = visit(expression);
+    return irBuilder.buildTypeOperator(value, type, isTypeTest: true);
   }
 
   @override
   ir.Primitive visitIsNot(ast.Send node,
                           ast.Node expression, DartType type, _) {
-    ir.Primitive receiver = visit(expression);
-    return irBuilder.buildTypeOperator(
-        receiver, type,
-        isTypeTest: true,
-        isNotCheck: true);
+    ir.Primitive value = visit(expression);
+    ir.Primitive check = irBuilder.buildTypeOperator(
+        value, type, isTypeTest: true);
+    return irBuilder.buildNegation(check);
   }
 
   ir.Primitive translateBinary(ast.Node left,
@@ -2307,7 +2303,7 @@ class GlobalProgramInformation {
     return cls.typeVariables.isNotEmpty && _backend.classNeedsRti(cls);
   }
 
-  Set<ClassElement> get interceptedClasses => _backend.interceptedClasses;
+  ClassElement get nullClass => _compiler.nullClass;
 }
 
 /// IR builder specific to the JavaScript backend, coupled to the [JsIrBuilder].