Mediaviewer easily allows 'save image as' -- when shared in secure-view mode

[jnweiger]

Seen in mediaviewer 1.0.5 and server 10.9.0 RC2

• enable richdocuments, and secure view
• admin shares folder 'photos_from_admin' to user alice with secure view
  

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• user alice accepts the share and clicks open an image to view to in mediaviewer
• mediaviewer shows a downward arrow for download, but that gives an error message. Okayish (maybe not even show the download ican?)
  

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• but photos are easily downloaded with a right click. BAD
  

Expected behaviour:

• There should be a transparent overlay that blocks download of the real image.

Not a regression :-)