[Enhancement] The cursor should have a Ø symbol in order to better represent the invalid action

[SoftVision-CiprianMuresan]

[Affected versions]:

• Firefox 54.0 and up

[Affected Platforms]:

• All Windows
• All Linux
• All Mac

[Steps to reproduce]:

1. Open the browser and navigate to https://send.dev.mozaws.net/.
2. Select a text and drag it on the Drop area.
3. Observe the cursor.

[Expected result]:

• The cursor is changed and shows a Ø symbol.

[Actual results]:

• Nothing happens.

[Notes]:

• As it stands now, some users might not understand why dropping text (or links, images) does not work, because there is no feedback for them.
• Here is a screen recording with the issue:
  

[ericawright]

I thought we had an alert for this, similar to when you drop a folder? If not, we probably should

[shrirambalaji]

I have some doubts on this, the issue requires that there is some sort of feedback when the user tries to upload an unsupported file, like a an alert of sorts? Please let me know if I am wrong. Thanks.

[dannycoates]

I think what we'd like to do here is change the cursor to a no-drop when they're dragging, a folder, more than one file, or something other than a file.

[shrirambalaji]

I have tried to solve the issue to some extent. Please review the recording

[dannycoates]

We won't fix this. We can't reliably change the cursor when dragging from off the page.