[Sync] Replace AttachmentIdSet with AttachmentIdList in interfaces.

sync/internal_api/attachments/attachment_service_impl.cc

Index: sync/internal_api/attachments/attachment_service_impl.cc
diff --git a/sync/internal_api/attachments/attachment_service_impl.cc b/sync/internal_api/attachments/attachment_service_impl.cc
index e76151507fa8f99543951c3f79b9354669e34d32..2db63c3634f53f359f84d4178060ce66e7ded4cf 100644
--- a/sync/internal_api/attachments/attachment_service_impl.cc
+++ b/sync/internal_api/attachments/attachment_service_impl.cc
@@ -273,14 +273,13 @@ void AttachmentServiceImpl::BeginUpload(const AttachmentId& attachment_id) {
 }
 
 void AttachmentServiceImpl::UploadAttachments(
-    const AttachmentIdSet& attachment_ids) {
+    const AttachmentIdList& attachment_ids) {
   DCHECK(CalledOnValidThread());
   if (!attachment_uploader_.get()) {
     return;
   }
-  AttachmentIdSet::const_iterator iter = attachment_ids.begin();
-  AttachmentIdSet::const_iterator end = attachment_ids.end();
-  for (; iter != end; ++iter) {
+  for (auto iter = attachment_ids.begin(); iter != attachment_ids.end();
+       ++iter) {
     upload_task_queue_->AddToQueue(*iter);
   }
 }