Move non-API code out of sync/api/attachments/

sync/api/attachments/attachment_downloader.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/attachment_downloader.h"
-
-#include "sync/internal_api/public/attachments/attachment_downloader_impl.h"
-
-namespace syncer {
-
-AttachmentDownloader::~AttachmentDownloader() {
-}
-
-// Factory function for creating AttachmentDownloaderImpl.
-// It is introduced to avoid SYNC_EXPORT-ing AttachmentDownloaderImpl since it
-// inherits from OAuth2TokenService::Consumer which is not exported.
-scoped_ptr<AttachmentDownloader> AttachmentDownloader::Create(
-    const GURL& sync_service_url,
-    const scoped_refptr<net::URLRequestContextGetter>&
-        url_request_context_getter,
-    const std::string& account_id,
-    const OAuth2TokenService::ScopeSet scopes,
-    scoped_ptr<OAuth2TokenServiceRequest::TokenServiceProvider>
-        token_service_provider) {
-  return scoped_ptr<AttachmentDownloader>(
-      new AttachmentDownloaderImpl(sync_service_url,
-                                   url_request_context_getter,
-                                   account_id,
-                                   scopes,
-                                   token_service_provider.Pass()));
-}
-
-}  // namespace syncer