Reviewed by Anders and Steve.

        Add a flag to DocLoader to prevent it from reloading 
        when performing a paste or drop operation.
        
        Remove m_cachePolicy from CachedResource as it is never used
        
        Fixes rdar://problem/5044366 : REGRESSION: Repro ASSERT failures 
        dragging image into GMail message in _web_writeImage and 
        documentFragmentFromDragData

        * editing/Editor.cpp:
        (WebCore::Editor::paste):
          prevent the docloader from reloading resources on paste
        * html/HTMLImageLoader.cpp:
        (WebCore::HTMLImageLoader::updateFromElement):
        * loader/Cache.cpp:
        (WebCore::createResource):
        * loader/CachedCSSStyleSheet.cpp:
        (WebCore::CachedCSSStyleSheet::CachedCSSStyleSheet):
        * loader/CachedCSSStyleSheet.h:
        * loader/CachedImage.cpp:
        (WebCore::CachedImage::CachedImage):
        * loader/CachedImage.h:
        * loader/CachedResource.cpp:
        (WebCore::CachedResource::CachedResource):
        * loader/CachedResource.h:
        * loader/CachedScript.cpp:
        (WebCore::CachedScript::CachedScript):
        * loader/CachedScript.h:
        * loader/CachedXBLDocument.cpp:
        (WebCore::CachedXBLDocument::CachedXBLDocument):
        * loader/CachedXBLDocument.h:
        * loader/CachedXSLStyleSheet.cpp:
        (WebCore::CachedXSLStyleSheet::CachedXSLStyleSheet):
        * loader/CachedXSLStyleSheet.h:
        * loader/DocLoader.cpp:
        (WebCore::DocLoader::DocLoader):
           Tidy up constructor initialise new field
        (WebCore::DocLoader::checkForReload):
           Prevent reload when pasting
        * loader/DocLoader.h:
        (WebCore::DocLoader::setPasteInProgress):
          new field and setter
        * page/DragController.cpp:
        (WebCore::DragController::concludeDrag):
          prevent the docloader from reloading resources on drop



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@20567 268f45cc-cd09-0410-ab3c-d52691b4dbfc