Store attachment crc in AttachmentStore

sync/internal_api/attachments/attachment_util.cc

Index: sync/internal_api/attachments/attachment_util.cc
diff --git a/sync/internal_api/attachments/attachment_util.cc b/sync/internal_api/attachments/attachment_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..08d7f997e0cb404af534f2a0d154a997f7919ebf
--- /dev/null
+++ b/sync/internal_api/attachments/attachment_util.cc
@@ -0,0 +1,16 @@
+// 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/attachment_util.h"
+
+#include "base/memory/ref_counted_memory.h"
+#include "third_party/leveldatabase/src/util/crc32c.h"
+
+namespace syncer {
+
+uint32_t ComputeCrc32c(const scoped_refptr<base::RefCountedMemory>& data) {
+  return leveldb::crc32c::Value(data->front_as<char>(), data->size());
+}
+
+}  // namespace syncer