[Sync] Add size and crc32c to AttachmentId.

sync/internal_api/attachments/fake_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/internal_api/public/attachments/fake_attachment_downloader.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "sync/internal_api/public/attachments/attachment_util.h"
 
 namespace syncer {
 
 FakeAttachmentDownloader::FakeAttachmentDownloader() {
 }
 
 FakeAttachmentDownloader::~FakeAttachmentDownloader() {
   DCHECK(CalledOnValidThread());
 }
 
 void FakeAttachmentDownloader::DownloadAttachment(
     const AttachmentId& attachment_id,
     const DownloadCallback& callback) {
   DCHECK(CalledOnValidThread());
   // This is happy fake downloader, it always successfully downloads empty
   // attachment.
   scoped_refptr<base::RefCountedMemory> data(new base::RefCountedBytes());
   scoped_ptr<Attachment> attachment;
-  const uint32_t crc32c = ComputeCrc32c(data);
   attachment.reset(
-      new Attachment(Attachment::CreateFromParts(attachment_id, data, crc32c)));
+      new Attachment(Attachment::CreateFromParts(attachment_id, data)));
   base::MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(callback, DOWNLOAD_SUCCESS, base::Passed(&attachment)));
 }
 
 }  // namespace syncer