dart2js: add builtin 'isSubtype'.

pkg/compiler/lib/src/js_emitter/old_emitter/emitter.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;
 
 
 class OldEmitter implements Emitter {
   final Compiler compiler;
   final CodeEmitterTask task;
@@ skipping 281 matching lines @@
       case JsBuiltin.typeName:
         return jsAst.js.expressionTemplateFor("#.$typeNameProperty");
 
       case JsBuiltin.rawRuntimeType:
         return jsAst.js.expressionTemplateFor("#.constructor");
 
       case JsBuiltin.createFunctionType:
         return backend.rti.representationGenerator
             .templateForCreateFunctionType;
 
+      case JsBuiltin.isSubtype:
+        // TODO(floitsch): move this closer to where is-check properties are
+        // built.
+        String isPrefix = namer.operatorIsPrefix;
+        return jsAst.js.expressionTemplateFor(
+            "('$isPrefix' + #) in #.prototype");
+
       default:
         compiler.internalError(NO_LOCATION_SPANNABLE,
             "Unhandled Builtin: $builtin");
         return null;
     }
   }
 
   List<jsAst.Statement> buildTrivialNsmHandlers(){
     return nsmEmitter.buildTrivialNsmHandlers();
   }
@@ skipping 1622 matching lines @@
     for (Element element in compiler.enqueuer.codegen.newlyEnqueuedElements) {
       if (element.isInstanceMember) {
         cachedClassBuilders.remove(element.enclosingClass);
 
         nativeEmitter.cachedBuilders.remove(element.enclosingClass);
 
       }
     }
   }
 }