Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/compiler.dart

 // Copyright (c) 2012, 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;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 88 matching lines @@
       : this.constantSystem = constantSystem;
 
   void initializeHelperClasses() {}
 
   void enqueueAllTopLevelFunctions(LibraryElement lib, Enqueuer world) {
     lib.forEachExport((Element e) {
       if (e.isFunction()) world.addToWorkList(e);
     });
   }
 
+  // TODO(karlklose): get rid of this and add a factory constructor to [List]
+  // that creates an instance of JSArray to make the dependency visible in from
+  // the source code.
+  void addBackendRtiDependencies(World world);
+
   void enqueueHelpers(ResolutionEnqueuer world);
   void codegen(CodegenWorkItem work);
 
   // The backend determines the native resolution enqueuer, with a no-op
   // default, so tools like dart2dart can ignore the native classes.
   native.NativeEnqueuer nativeResolutionEnqueuer(world) {
     return new native.NativeEnqueuer();
   }
   native.NativeEnqueuer nativeCodegenEnqueuer(world) {
     return new native.NativeEnqueuer();
@@ skipping 1033 matching lines @@
 
   void close() {}
 
   toString() => name;
 
   /// Convenience method for getting an [api.CompilerOutputProvider].
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }