Comment 15 for bug 1444110

This began at the below commit.
Adding Cc: to <email address hidden>; Could you possibly take a look at this one? Thanks

    commit 9a568c41ccd1ccf6073758973da5914a44f629d2
    Author: Eike Rathke <email address hidden>
    AuthorDate: Fri Dec 5 21:32:06 2014 +0100
    Commit: Eike Rathke <email address hidden>
    CommitDate: Fri Dec 5 21:40:27 2014 +0100

        Ctrl+A and Data Sort took ages to broadcast ALL cells

        ... now that also empty cells are to be broadcasted.

        Set dirty and broadcast only the effective data range as determined by Sort.

        This is more a workaround, a cleaner solution would be to refactor the
        SetDirty() algorithm to iterate only through broadcasters and use
        AreaBroadcast() to notify area listeners.

        However, this can also be easily backported to 4-3.

        Change-Id: I6d68ca0088cec6a8328a3e93364ac928ef69babe