Do not update AttachmentIds after uploading attachments to sync server.

sync/api/attachments/attachment_uploader.h

Index: sync/api/attachments/attachment_uploader.h
diff --git a/sync/api/attachments/attachment_uploader.h b/sync/api/attachments/attachment_uploader.h
index 12fe1a308ad0fbe0438df55ac9feed66f8e22cb6..4774451d53faeebbffa313bed821f101261e443f 100644
--- a/sync/api/attachments/attachment_uploader.h
+++ b/sync/api/attachments/attachment_uploader.h
@@ -34,8 +34,8 @@ class SYNC_EXPORT AttachmentUploader {
   // |callback| will be invoked when the operation has completed (successfully
   // or otherwise).
   //
-  // |callback| will receive an UploadResult code and an updated AttachmentId
-  // containing the server address of the newly uploaded attachment.
+  // |callback| will receive an UploadResult code and the AttachmentId of the
+  // newly uploaded attachment.
   virtual void UploadAttachment(const Attachment& attachment,
                                 const UploadCallback& callback) = 0;
 };