Determines if a link being dragged can be dropped and returns true if so.
aEvent should be a dragenter or dragover event.
If aAllowSameDocument is false, drops are only allowed if the document
of the source of the drag is different from the destination. This check
includes any parent, sibling and child frames in the same content tree.
If true, the source is not checked.
Given a drop event aEvent, determines the link being dragged and returns
it. If a uri is returned the caller can, for instance, load it. If null
is returned, there is no valid link to be dropped.
A NS_ERROR_DOM_SECURITY_ERR error will be thrown and the event cancelled if
the receiving target should not load the uri for security reasons. This
will occur if any of the following conditions are true:
- the source of the drag initiated a link for dragging that
it itself cannot access. This prevents a source document from tricking
the user into a dragging a chrome url, for example.
- aDisallowInherit is true, and the URI being dropped would inherit the
current document’s security context (URI_INHERITS_SECURITY_CONTEXT).
aName is filled in with the link title if it exists, or an empty string
otherwise.