Roll kernel to latest

pkg/compiler/lib/src/js_backend/backend.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.
 
 library js_backend.backend;
 
 import 'dart:async' show Future;
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
 
@@ skipping 2352 matching lines @@
     if (!enqueuer.queueIsEmpty) return false;
 
     noSuchMethodRegistry.onQueueEmpty();
     if (!enabledNoSuchMethod &&
         (noSuchMethodRegistry.hasThrowingNoSuchMethod ||
             noSuchMethodRegistry.hasComplexNoSuchMethod)) {
       enableNoSuchMethod(enqueuer);
       enabledNoSuchMethod = true;
     }
 
-    if (compiler.options.useKernel) {
+    if (compiler.options.useKernel && compiler.mainApp != null) {
       kernelTask.buildKernelIr();
     }
 
     if (compiler.options.hasIncrementalSupport) {
       // Always enable tear-off closures during incremental compilation.
       Element e = helpers.closureFromTearOff;
       if (e != null && !enqueuer.isProcessed(e)) {
         registerBackendUse(e);
         enqueuer.addToWorkList(e);
       }
@@ skipping 881 matching lines @@
   ClassElement get mapImplementation => helpers.mapLiteralClass;
   ClassElement get constMapImplementation => helpers.constMapLiteralClass;
   ClassElement get typeImplementation => helpers.typeLiteralClass;
   ClassElement get boolImplementation => helpers.jsBoolClass;
   ClassElement get nullImplementation => helpers.jsNullClass;
   ClassElement get syncStarIterableImplementation => helpers.syncStarIterable;
   ClassElement get asyncFutureImplementation => helpers.futureImplementation;
   ClassElement get asyncStarStreamImplementation => helpers.controllerStream;
   ClassElement get functionImplementation => helpers.coreClasses.functionClass;
 }