Fixed: <rdar://problem/4029010> Expose method to retrieve drag image for WebView...

	Fixed: <rdar://problem/4029010> Expose method to retrieve drag image for WebView's selection

        Reviewed by sullivan.

        * WebView.subproj/WebHTMLView.m:
        (-[WebHTMLView _startDraggingImage:at:operation:event:sourceIsDHTML:DHTMLWroteData:]): call _selectionDraggingImage
        (-[WebHTMLView _selectionDraggingImage]): new SPI for Mail, factored from previous method
        (-[WebHTMLView _selectionDraggingRect]): new SPI for Mail
        * WebView.subproj/WebHTMLViewPrivate.h:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8763 268f45cc-cd09-0410-ab3c-d52691b4dbfc