Reviewed by Oliver Hunt.

        Remove layoutTestController.addFileToPasteboardOnDrag and add eventSender.beginDragWithFiles
        https://bugs.webkit.org/show_bug.cgi?id=25852

        This allows us to now test multi-file file drags in DumpRenderTree per:
        https://bugs.webkit.org/show_bug.cgi?id=25862

        I removed the existing tests using addFileToPasteboardOnDrag()
        and replaced them with a new test (editing/pasteboard/file-input-files-access)
        which covers several more drag-drop cases.

        I added a DumpRenderTreeFileDraggingSource class to avoid
        the hack of if (!draggingSource) in [DumpRenderTreeDraggingInfo draggingSourceOperationMask]

        New Test: editing/pasteboard/file-input-files-access.html

        * DumpRenderTree/DumpRenderTree.xcodeproj/project.pbxproj:
        * DumpRenderTree/DumpRenderTreeFileDraggingSource.h: Added.
        * DumpRenderTree/DumpRenderTreeFileDraggingSource.m: Added.
        (-[DumpRenderTreeFileDraggingSource draggingSourceOperationMaskForLocal:]):
        * DumpRenderTree/LayoutTestController.cpp:
        (LayoutTestController::LayoutTestController):
        (LayoutTestController::staticValues): removed addFileToPasteboardOnDrag support
        (LayoutTestController::staticFunctions): removed addFileToPasteboardOnDrag support
        * DumpRenderTree/LayoutTestController.h:
        * DumpRenderTree/mac/DumpRenderTree.mm:
        (runTest): ASSERT that draggingInfo has been cleared
        * DumpRenderTree/mac/EventSendingController.mm:
        (+[EventSendingController isSelectorExcludedFromWebScript:]): Sorted selectors.
        (+[EventSendingController webScriptNameForSelector:]): Sorted selectors.
        (-[EventSendingController beginDragWithFiles:]):
        (-[EventSendingController mouseMoveToX:Y:]):
        (-[EventSendingController keyDown:withModifiers:]):
        (-[EventSendingController fireKeyboardEventsToElement:]): removed spurious { }
        * DumpRenderTree/mac/UIDelegate.mm:
        (-[UIDelegate webView:dragImage:at:offset:event:pasteboard:source:slideBack:forView:]): removed addFileToPasteboardOnDrag support

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@43890 268f45cc-cd09-0410-ab3c-d52691b4dbfc