Executes theFDownloadFileoperation, but unlike theExecutemethod this can be called from a background thread, this works becauseFDownloadFileis thread safe and it does not change the state of source control. NOTE: This is only intended for use by the virtualization module and will be deprecated at some point in the future when thread safety is built into the system. NOTE: This is only implemented for the perforce source control provider with no plans to extend this to other providers.