- remove "loading" flag from WebDataSource and code that manages it; it is redundat.

        * Loader/WebFrameLoader.m:
        (-[WebFrameLoader addPlugInStreamLoader:]):
        (-[WebFrameLoader removePlugInStreamLoader:]):
        (-[WebFrameLoader addSubresourceLoader:]):
        (-[WebFrameLoader removeSubresourceLoader:]):
        * WebView/WebDataSource.m:
        (-[WebDataSourcePrivate dealloc]):
        (-[WebDataSource _setPrimaryLoadComplete:]):
        (-[WebDataSource _stopLoading]):
        (-[WebDataSource _prepareForLoadStart]):
        (-[WebDataSource _startLoading]):
        (-[WebDataSource isLoading]):
        * WebView/WebDataSourceInternal.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@15986 268f45cc-cd09-0410-ab3c-d52691b4dbfc