cps-ir: Implement type tests for interface types without type arguments.

pkg/compiler/lib/src/js_backend/backend.dart

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index 7def6be498043d7a006c81f2b43635c8999b6ab1..aeb4fb83d503180aa0b7cc191ed501e59e7bbde9 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -1642,6 +1642,18 @@ class JavaScriptBackend extends Backend {
         element == jsFixedArrayClass;
   }
 
+  /// Return [true] if the class is represented by a native JavaSCript type in
+  /// the generated code.
+  bool isNativePrimitiveType(ClassElement cls ) {
+    // TODO(karlklose): cleanup/merge with hasDirectCheck, when the rest of the
+    // checks are implemented in the CPS IR.
+    return cls == compiler.intClass ||
+        cls == compiler.numClass ||
+        cls == compiler.doubleClass ||
+        cls == compiler.boolClass ||
+        cls == compiler.stringClass;
+  }
+
   bool mayGenerateInstanceofCheck(DartType type) {
     // We can use an instanceof check for raw types that have no subclass that
     // is mixed-in or in an implements clause.