[Mac] Make Clipboard::createDragImage non-virtual
https://bugs.webkit.org/show_bug.cgi?id=116136

Reviewed by Benjamin Poulain.

* dom/Clipboard.h: Made createDragImage non-virtual for non-legacy.

* platform/mac/ClipboardMac.h: Removed frame argument from create function
and constructor. Removed createDragImage and dragNSImage. Removed m_frame
data member.

* platform/mac/ClipboardMac.mm:
(WebCore::ClipboardMac::ClipboardMac): Removed frame argument and code
to initialize m_frame.
(WebCore::Clipboard::createDragImage): Merged the createDragImage and
dragNSImage functions, since they were the same thing. Changed code to get
the frame from the drag image element. Made the createDragImage function
a Clipboard member instead of ClipboardMac.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150107 268f45cc-cd09-0410-ab3c-d52691b4dbfc