smbprovider: Add MountConfigProto to directory_entry - Added MountConfigProto since MountConfig options will be passed from chrome-side. BUG=chromium:888096 TEST=emerges Change-Id: Ia5514b53b4070738aeb9ff1b55f212d9b90071ec Reviewed-on: https://chromium-review.googlesource.com/1239199 Commit-Ready: jimmy gong <[email protected]> Tested-by: jimmy gong <[email protected]> Reviewed-by: Zentaro Kavanagh <[email protected]>