Always enable RTI for incremental compilation.

dart/pkg/dart2js_incremental/lib/caching_compiler.dart

 // Copyright (c) 2013, 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_incremental;
 
 /// Do not call this method directly. It will be made private.
 // TODO(ahe): Make this method private.
 Future<Compiler> reuseCompiler(
     {DiagnosticHandler diagnosticHandler,
@@ skipping 47 matching lines @@
     oldTag.makeCurrent();
     compiler = new Compiler(
         inputProvider,
         outputProvider,
         diagnosticHandler,
         libraryRoot,
         packageRoot,
         options,
         environment);
     JavaScriptBackend backend = compiler.backend;
+
     // Much like a scout, an incremental compiler is always prepared. For
     // mixins, at least.
     backend.emitter.oldEmitter.needsMixinSupport = true;
-    return new Future.value(compiler);
+
+    Uri core = Uri.parse("dart:core");
+    return compiler.libraryLoader.loadLibrary(core).then((_) {
+      // Likewise, always be prepared for runtimeType support.
+      // TODO(johnniwinther): Add global switch to force RTI.
+      compiler.enabledRuntimeType = true;
+      backend.registerRuntimeType(
+          compiler.enqueuer.resolution, compiler.globalDependencies);
+      return compiler;
+    });
   } else {
     for (final task in compiler.tasks) {
       if (task.watch != null) {
         task.watch.reset();
       }
     }
     compiler
         ..outputProvider = outputProvider
         ..provider = inputProvider
         ..handler = diagnosticHandler
@@ skipping 69 matching lines @@
             library.isPlatformLibrary ||
             (packagesAreImmutable && library.isPackageLibrary));
       };
     }
     return compiler.libraryLoader.resetAsync(reuseLibrary).then((_) {
       oldTag.makeCurrent();
       return compiler;
     });
   }
 }