Add AttachmentUploader interface and fake implementation.

sync/api/attachments/attachment_uploader.h

+// 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.
+
+#ifndef SYNC_API_ATTACHMENTS_ATTACHMENT_UPLOADER_H_
+#define SYNC_API_ATTACHMENTS_ATTACHMENT_UPLOADER_H_
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "sync/api/attachments/attachment.h"
+#include "sync/base/sync_export.h"
+
+namespace syncer {
+
+// AttachmentUploader is responsible for uploading attachments to the server.
+class SYNC_EXPORT AttachmentUploader {
+ public:
+  // The result of an UploadAttachment operation.
+  enum UploadResult {
+    UPLOAD_SUCCESS,            // No error, attachment was uploaded
+                               // successfully.
+    UPLOAD_UNSPECIFIED_ERROR,  // An unspecified error occurred.
+  };
+
+  typedef base::Callback<void(const UploadResult&, const AttachmentId&)>
+      UploadCallback;
+
+  AttachmentUploader();
+  virtual ~AttachmentUploader();
+
+  // Upload |attachment| and invoke |callback| when done.
+  //
+  // |callback| will be invoked when the operation has completed (successfully
+  // or otherwise).
+  //
+  // |callback| will receive an UploadResult code and an updated AttachmentId
+  // |containing the server address of the newly uploaded attachment.
+  virtual void UploadAttachment(const Attachment& attachment,
+                                const UploadCallback& callback) = 0;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_API_ATTACHMENTS_ATTACHMENT_UPLOADER_H_