Reviewed by Adam.
WebCore:
        More drag and drop migration, now the entirety of the
        drag initiation logic has been rendered platform independent
        This has required a number of new interfaces, and a reasonable
        amount of logic migration.

        As a side effect, this patch also fixes rdar://problem/4945341

        There are some basic Qt stubs that should stop the build from failing,
        however the absence of ClipboardQt means any attempt to initiate a drag 
        may cause a crash.

        * WebCore.exp:
           Exporting new symbols

        * WebCore.xcodeproj/project.pbxproj:
           New files

        * dom/Clipboard.cpp:
        (WebCore::Clipboard::canSaveAsWebArchive):
          Migrated from WebKit

        * dom/Clipboard.h:
          Added more methods to allow Clipboard to be used as a 
          platform independent container for drag and drop

        * page/DragClient.h:
        (WebCore::DragClient::declareAndWriteDragImage):
          This is a mac only helper function, so i've made it have an empty implementation,
          that way we won't need a PLATFORM(MAC) block in SVGImageEmptyClients

        * page/DragController.cpp:
        (WebCore::DragController::dragExited):
        (WebCore::DragController::performDrag):
        (WebCore::DragController::tryDocumentDrag): 
        (WebCore::DragController::tryDHTMLDrag):
          Using RefPtrs now
        (WebCore::getCachedImage):
        (WebCore::getImage):
          Helper functions                   
        (WebCore::dragLocForDHTMLDrag):
        (WebCore::dragLocForSelectionDrag):
        (WebCore::DragController::startDrag):
        (WebCore::DragController::doImageDrag):
        (WebCore::DragController::doSystemDrag):
          Logic that generates drag images and clipboard content, and
          initiates the actual system drag operation

        * page/DragController.h:
          Method and variable declarations

        * page/EventHandler.cpp:
        (WebCore::EventHandler::handleDrag):
          handleDrag is now platform independent
        (WebCore::EventHandler::handleTextInputEvent):
           formatting

        * page/EventHandler.h:
        (WebCore::EventHandler::eventLoopHandleMouseDragged):
          Forgot to define this stub function 

        * page/Frame.h:
          Declaring dragImageForSelection to provide drag image for selected content

        * page/mac/DragControllerMac.mm:
          Defining drag images control vars

        * page/mac/EventHandlerMac.mm:
        (WebCore::EventHandler::createDraggingClipboard):
          Migrated old clipboard creation to here

        * page/mac/FrameMac.mm:
        (WebCore::Frame::dragImageForSelection):
          Wrap FrameMac::selectionImage

        * page/qt/DragControllerQt.cpp:
          Defining drag images control vars

        * page/qt/EventHandlerQt.cpp:
        (WebCore::EventHandler::createDraggingClipboard):
          stub

        * page/qt/FrameQt.cpp:
        (WebCore::Frame::dragImageForSelection):
          stub

        * platform/DragImage.cpp: Added.
        (WebCore::fitDragImageToMaxSize):
        (WebCore::createDragImageForSelection):
           Platform independent processing for drag images

        * platform/DragImage.h: Added.
           Declaring typedefs and wrapper functions to abstract the handling
           of drag images 

        * platform/Pasteboard.h:
          Declaring extracted writeURL and writeSelection methods

        * platform/graphics/svg/SVGImageEmptyClients.h:
        (WebCore::SVGEmptyDragClient::willPerformDragSourceAction):
        (WebCore::SVGEmptyDragClient::startDrag):
        (WebCore::SVGEmptyDragClient::createDragImageForLink):
          Stubs FTW!

        * platform/mac/ClipboardMac.h:
        (WebCore::ClipboardMac::pasteboard):
          Provide accessor for underlying NSPasteboard

        * platform/mac/ClipboardMac.mm:
        (WebCore::ClipboardMac::hasData):
        (WebCore::ClipboardMac::writeRange):
        (WebCore::ClipboardMac::writeURL):
        (WebCore::ClipboardMac::declareAndWriteDragImage):
        (WebCore::ClipboardMac::createDragImage):
           Implemented new Clipboarid functionality.
        (WebCore::ClipboardMac::dragNSImage):
           Made this a const method

        * platform/mac/DragImageMac.mm: Added.
        (WebCore::dragImageSize):
        (WebCore::deleteDragImage):
        (WebCore::scaleDragImage):
        (WebCore::dissolveDragImageToFraction):
        (WebCore::createDragImageFromImage):
        (WebCore::createDragImageIconForCachedImage):
           Implemented platform specific DragImage functions

        * platform/mac/PasteboardMac.mm:
        (WebCore::writeSelection):
        (WebCore::Pasteboard::writeSelection):
        (WebCore::writeURL):
        (WebCore::Pasteboard::writeURL):
           Extracted member implementations of these functions, so that
           Clipboard could also make use of this functionality.
           Pasteboard methods now call the new non-member implementations.
           Also fixed implementations to respect the list of requested types.

        * platform/qt/DragImageQt.cpp: Added.
        (WebCore::dragImageSize):
        (WebCore::deleteDragImage):
        (WebCore::scaleDragImage):
        (WebCore::dissolveDragImageToFraction):
        (WebCore::createDragImageFromImage):
        (WebCore::createDragImageIconForCachedImage):  
          Stubs

WebKit:
        Moving the drag initiation logic to WebCore.
        The redundant code in webkit will be moved out in a later patch.

        * WebCoreSupport/WebDragClient.h:
        * WebCoreSupport/WebDragClient.mm:
        (getTopHTMLView):
          Helper function
        (WebDragClient::willPerformDragSourceAction):
        (WebDragClient::startDrag):
        (WebDragClient::createDragImageForLink):
          Implemented new DragClient methods
        (WebDragClient::declareAndWriteDragImage):
          Helper function for the Mac to allow new drag and drop
          code to match behaviour
          
        * WebView/WebHTMLView.mm:
        (-[WebHTMLView _dragImageForURL:withLabel:]):
        (-[WebHTMLView _dragImageForLinkElement:]):
          Refactoring old _dragImageForLinkElement function so that 
          the link drag image can be created with just a URL and label, 
          rather than requiring the original element
        (-[WebHTMLView dragImage:at:offset:event:pasteboard:source:slideBack:]):
          Removed logic that is no longer necessary                 
        (-[WebHTMLView _mouseDownEvent]):
          The WebDragClient may need the original mouseDownEvent of a drag when initiating
          a drag
        * WebView/WebHTMLViewInternal.h:
          Declaring _mouseDownEvent

        * WebView/WebHTMLViewPrivate.h:
          Declaring _dragImageForURL
                                        
      


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@19689 268f45cc-cd09-0410-ab3c-d52691b4dbfc