Port sky_shell to Linux for testing

sky/shell/linux/platform_service_provider_linux.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 "base/bind.h"
+#include "base/trace_event/trace_event.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+#include "sky/shell/service_provider.h"
+
+namespace sky {
+namespace shell {
+
+mojo::ServiceProviderPtr CreateServiceProvider(
+    ServiceProviderContext* context) {
+  mojo::MessagePipe pipe;
+  // TODO(abarth): Wire pipe.handle1 up to something.
+  return mojo::MakeProxy(
+      mojo::InterfacePtrInfo<mojo::ServiceProvider>(pipe.handle0.Pass(), 0u));
+}
+
+}  // namespace shell
+}  // namespace sky