linux_aura: Implement file drag and drop in content area.

linux_aura: Implement file drag and drop in content area.

In OSExchangeData, there's a difference between URLs and files. In the
mime type "text/uri-list", there isn't, and Linux usually uses the later
to exchange both data types.

This fixes dragging files onto several sites, like the HTML Five Wow
Terminal, but doesn't fix Dropbox, which seems to be failing somewhere
else.

BUG=317548
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243840

[sky, 2014-01-09 00:26:56]

LGTM

[commit-bot: I haz the power, 2014-01-09 00:33:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/erg@chromium.org/129113004/1

[commit-bot: I haz the power, 2014-01-09 10:48:59]

Change committed as 243840