build kernel for the entire program after resolution

pkg/compiler/lib/src/js_backend/kernel_task.dart

+// Copyright (c) 2016, 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.
+
+import '../compiler.dart';
+import '../kernel/kernel.dart';
+
+import 'backend.dart';
+
+/// Visits the compiler main function and builds the kernel representation.
+///
+/// This creates a mapping from kernel nodes to AST nodes to be used later.
+class KernelTask {
+  final Compiler _compiler;
+  final Kernel kernel;
+
+  KernelTask(JavaScriptBackend backend)
+      : this._compiler = backend.compiler,
+        this.kernel = new Kernel(backend.compiler);
+
+  void onQueueEmpty() {
+    kernel.functionToIr(_compiler.mainFunction);
+    kernel.processWorkQueue();
+  }
+}