Add skeleton of SSAKernel function compiler

pkg/compiler/lib/src/ssa/builder_kernel.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 '../common/codegen.dart' show CodegenWorkItem;
+import '../common/tasks.dart' show CompilerTask;
+import '../io/source_information.dart';
+import '../js_backend/backend.dart' show JavaScriptBackend, FunctionCompiler;
+import '../elements/elements.dart';
+
+import 'nodes.dart';
+
+class SsaKernelBuilderTask extends CompilerTask {
+  final JavaScriptBackend backend;
+  final SourceInformationStrategy sourceInformationFactory;
+
+  String get name => 'SSA kernel builder';
+
+  SsaKernelBuilderTask(JavaScriptBackend backend, this.sourceInformationFactory)
+      : super(backend.compiler.measurer);
+
+  HGraph build(CodegenWorkItem work) {
+    return measure(() {
+      Element element = work.element.implementation;
+      throw "unimplemented";
+    });
+  }
+}