Add AttachmentUploader interface and fake implementation.

sync/api/attachments/fake_attachment_uploader.cc

+// Copyright 2014 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 "sync/api/attachments/fake_attachment_uploader.h"
+
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "sync/api/attachments/attachment.h"
+
+namespace syncer {
+
+FakeAttachmentUploader::FakeAttachmentUploader() {
+  DCHECK(CalledOnValidThread());
+}
+
+FakeAttachmentUploader::~FakeAttachmentUploader() {
+  DCHECK(CalledOnValidThread());
+}
+
+void FakeAttachmentUploader::UploadAttachment(const Attachment& attachment,
+                                              const UploadCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  UploadResult result = UPLOAD_SUCCESS;
+  AttachmentId updated_id = attachment.GetId();
+  // TODO(maniscalco): Update the attachment id with server address information
+  // before passing it to the callback.
+  base::MessageLoop::current()->PostTask(
+      FROM_HERE, base::Bind(callback, result, updated_id));
+}
+
+}  // namespace syncer