https://bugs.webkit.org/show_bug.cgi?id=52343
<rdar://problem/7660558>
               
Reviewed by Darin Adler.

This patch contains the changes required to support dropping content
in WebKit on the Mac. The DragData class has been extended to provide
additional context from the application (keyboard state, modal windows, etc.)
as well as information of the drag pasteboard being used.
The support for WebKit as drag source will be added with a separate patch.

* WebCore.exp.in:
* page/DragController.cpp:
(WebCore::DragController::dragIsMove): Added DragData parameter.
(WebCore::DragController::tryDocumentDrag): Modified call to dragIsMove.
(WebCore::DragController::concludeEditDrag): Same as above.
* page/DragController.h: Added parameter to isCopyKeyDown.
* page/mac/DragControllerMac.mm:
The following methods have been modified to use the information stored
in the DragData class.
(WebCore::DragController::isCopyKeyDown):
(WebCore::DragController::dragO...