[Sync] Rewriting ".reset(new" pattern to use "= base::MakeUnique" instead.

components/sync/engine/attachments/on_disk_attachment_store.cc

Index: components/sync/engine/attachments/on_disk_attachment_store.cc
diff --git a/components/sync/engine/attachments/on_disk_attachment_store.cc b/components/sync/engine/attachments/on_disk_attachment_store.cc
index e9aa3c00f27fe4e73c5f05f220f26db907b34406..4afc78b5a356559d6dc2386ac8b878b2da46f866 100644
--- a/components/sync/engine/attachments/on_disk_attachment_store.cc
+++ b/components/sync/engine/attachments/on_disk_attachment_store.cc
@@ -12,6 +12,7 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/location.h"
+#include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/sequenced_task_runner.h"
 #include "components/sync/engine/attachments/attachment_util.h"
@@ -435,8 +436,8 @@ std::unique_ptr<Attachment> OnDiskAttachmentStore::ReadSingleAttachment(
       return attachment;
     }
   }
-  attachment.reset(
-      new Attachment(Attachment::CreateFromParts(attachment_id, data)));
+  attachment = base::MakeUnique<Attachment>(
+      Attachment::CreateFromParts(attachment_id, data));
   return attachment;
 }