Revert 169711 "Prevent web content from forging File entries in ..."

Revert 169711 "Prevent web content from forging File entries in ..."

As it turns out, we only needed to patch the Chrome side.

> Prevent web content from forging File entries in drag and drop.
> 
> There are two separate bugs that this and the corresponding Chrome patch
> aim to address:
> - On Linux, files and URLs are transferred in the same MIME type, so
>   it's impossible to tell if a filename was set by a trusted source or
>   forged by web content.
> - DownloadURL triggers the download of potentially cross-origin content.
>   On some platforms, such as Windows, the resulting download is treated
>   as a file drag by Chrome, allowing web content to read cross origin
>   content.
> 
> In order to prevent web content from doing this, drags initiated by a
> renderer will be marked as tainted. When tainted drags are over web
> content, Blink will only allow the resulting filename to be used for
> navigation, with Chrome enforcing this with the sandbox policy.
> 
> Unfortunately, this does break some potentially interesting use cases
> like being able to drag an attachment from Gmail to a file input, but
> those will have to be separately addressed, if possible.
> 
> BUG=346135
> R=abarth@chromium.org, tony@chromium.org
> 
> Review URL: https://codereview.chromium.org/193803002

TBR=dcheng@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=169979

[dcheng, 2014-03-25 22:14:54]

Committed patchset #1 manually as r169979.