fix(files): Not-yet-downloaded files can be opened via double click

Fixes T4840

internal_packages/attachments/lib/attachment-component.cjsx

@@ -54,7 +54,7 @@ class AttachmentComponent extends React.Component
 
   _canAbortDownload: -> true
 
-  _canClickToView: => not @props.removable and not @_isDownloading()
+  _canClickToView: => not @props.removable
 
   _isDownloading: => @props.download?.state is "downloading"
 
@@ -74,7 +74,8 @@ class AttachmentComponent extends React.Component
       event.preventDefault()
     return
 
-  _onClickView: => Actions.fetchAndOpenFile(@props.file) if @_canClickToView()
+  _onClickView: =>
+    Actions.fetchAndOpenFile(@props.file) if @_canClickToView()
 
   _onClickRemove: (event) =>
     Actions.removeFile

src/flux/stores/file-download-store.coffee

@@ -68,12 +68,12 @@ class Download
       # a callback until the stream has ended. These helper functions ensure
       # that resolve or reject is only fired once regardless of the order
       # these two events (stream end and `success`) happen in.
-      streamEnded = ->
+      streamEnded = =>
         finished = true
         if finishedAction
           finishedAction(@)
 
-      onStreamEnded = (action) ->
+      onStreamEnded = (action) =>
         if finished
           action(@)
         else