Cannot load a font from an other wiki when multi-wiki is "domain based"

Because of http://en.wikipedia.org/wiki/Cross-origin_resource_sharing

See XWIKI-11300 for more details.

Example of affected use cases:

• a CSS loads a font stored in an attachment of a page of an other wiki.

  @font-face{
  	font-family:'My Font';
  	src:url('$docOfAnOtherWiki.getAttachmentURL("myfont.eot")')
  }
  

• XWIKI-11300: a CSS stored in an other wiki loads a font resource (via getSkinFile() or webjar).