Support user generated custom native JS classes.

pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter;
 
 // Function signatures used in the generation of runtime type information.
 typedef void FunctionTypeSignatureEmitter(Element method,
                                           FunctionType methodType);
 
@@ skipping 50 matching lines @@
     assert(invariant(classElement, classElement.isDeclaration));
 
     TypeTestProperties result = new TypeTestProperties();
 
     /// Generates an is-test if the test is not inherited from a superclass
     /// This assumes that for every class an is-tests is generated
     /// dynamically at runtime. We also always generate tests against
     /// native classes.
     /// TODO(herhut): Generate tests for native classes dynamically, as well.
     void generateIsTest(Element other) {
-      if (classElement.isNative ||
+      if (classElement.isJsInterop || classElement.isNative ||
           !classElement.isSubclassOf(other)) {
         result.properties[namer.operatorIs(other)] = js('1');
       }
     }
 
     void generateFunctionTypeSignature(FunctionElement method,
                                        FunctionType type) {
       assert(method.isImplementation);
       jsAst.Expression thisAccess = new jsAst.This();
       ClosureClassMap closureData =
@@ skipping 231 matching lines @@
               js.number(index));
     }
     jsAst.Expression convertRtiToRuntimeType = backend.emitter
          .staticFunctionAccess(backend.findHelper('convertRtiToRuntimeType'));
 
     return new StubMethod(name,
                           js('function () { return #(#) }',
                              [convertRtiToRuntimeType, computeTypeVariable]));
   }
 }