Reviewed by Maciej.

    Reviewed by Maciej.

        - fix <rdar://problem/5310848> WebDataSource lifetime problem -- may be cause of the leaks seen on the buildbot

        * WebView/WebDataSource.mm:
        (-[WebDataSourcePrivate dealloc]): Added a call to the new detachDataSource function.
        (-[WebDataSourcePrivate finalize]): Ditto.

        * WebView/WebDocumentLoaderMac.h: Added detachDataSource function to be used when the
        WebDataSource is deallocated. Added retain/releaseDataSource helper functions to be
        used to retain and release the data source object. Replaced the m_hasEverBeenDetached
        boolean with a more primitive and hence easier to understand m_isDataSourceRetained boolean.

        * WebView/WebDocumentLoaderMac.mm:
        (WebDocumentLoaderMac::WebDocumentLoaderMac): Initialize m_isDataSourceRetained to false.
        (WebDocumentLoaderMac::setDataSource): Call retainDataSource instead of calling HardRetain
        on the dataSource parameter. Also updated a comment.
        (WebDocumentLoaderMac::attachToFrame): Call retainDataSource unconditionally rather than
        trying to use m_hasEverBeenDetached to decide if a retain is needed. Also got rid of an
        assertion that m_loadingResources is empty -- not important any more.
        (WebDocumentLoaderMac::detachFromFrame): Call releaseDataSource instead of using
        HardRelease, but only if m_loadingResources is empty. If it's non-empty, then we'll
        do the releaseDataSource later in decreaseLoadCount.
        (WebDocumentLoaderMac::increaseLoadCount): Call retainDataSource unconditionally
        rather than calling HardRetain only if the old set of resources was empty.
        (WebDocumentLoaderMac::decreaseLoadCount): Call releaseDataSource if m_loadingResources
        is empty and we're not attached to a frame. If we are attached to a frame, then
        we'll do the releaseDataSource later in detachFromFrame.
        (WebDocumentLoaderMac::retainDataSource): Added. Calls CFRetain, but only if the data
        source is not already retained (according to the boolean).
        (WebDocumentLoaderMac::releaseDataSource): Added. Calls CFRelease, but only if the data
        source is currently retained (according to the boolean).
        (WebDocumentLoaderMac::detachDataSource): Added. Sets m_dataSource to nil. Since this
        is only called from WebDataSource's dealloc and finalize methods, it won't ever be called
        when the m_isDataSourceRetained boolean is true.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@23957 268f45cc-cd09-0410-ab3c-d52691b4dbfc