Specifically, this line should use std::move to avoid bumping the reference count, and thus making a copy.

As part of this change, we should consider adding some infrastructure to enable us to test cases like this in the future.

redbeard0531 suggested adding a global callback, which is called each time we make a copy, here. For example, that method could call something like kGlobalDocumentCopyCallBack.copyMade(), and we could use that global struct/class to assert that no copies were made. If we go this route, we should also consider attaching this to the service context.