Port sky_shell to Linux for testing

sky/shell/service_provider.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sky/shell/service_provider.h"
+
+#include "base/single_thread_task_runner.h"
+
+namespace sky {
+namespace shell {
+
+ServiceProviderContext::ServiceProviderContext(
+    scoped_refptr<base::SingleThreadTaskRunner> runner)
+      : platform_task_runner(runner.Pass()) {}
+
+ServiceProviderContext::~ServiceProviderContext() {
+}
+
+}  // namespace shell
+}  // namespace sky