Add 'source' to QRSetFile event.

src/Posting/QR.coffee

@@ -340,8 +340,9 @@ QR =
     $.event 'QRFile', QR.selected?.file
 
   setFile: (e) ->
-    {file, name} = e.detail
-    file.name = name if name?
+    {file, name, source} = e.detail
+    file.name   = name   if name?
+    file.source = source if source?
     QR.open()
     QR.handleFiles [file]
 

src/Posting/QR.post.coffee

@@ -319,6 +319,10 @@ QR.post = class
     else
       $.rmClass QR.nodes.oekaki,     'has-file'
       $.rmClass QR.nodes.fileSubmit, 'has-file'
+    if @file?.source?
+      QR.nodes.fileSubmit.dataset.source = @file.source
+    else
+      QR.nodes.fileSubmit.removeAttribute 'data-source'
     QR.nodes.spoiler.checked = @spoiler
 
   updateFlashURL: ->