Also a bit of cleanup around log tags and DownloadRequest. Change-Id: I33221f099ed691e5258e1741cf0a63381404f520
This is a straight up copy of the AttachmentDownloadService and a rename. All the future Attachment work will be done in this class and we'll flip the switch when it is ready. Change-Id: I2990cbfd1f7c8e2946c155ea1c124223d0f47ff9