Reviewed by Maciej

    Reviewed by Maciej

        Fix for this bug:

        <rdar://problem/3890955> 8A314: Forward delete sometimes fails to delete the selected quoted text

        * khtml/editing/htmlediting.cpp:
        (khtml::DeleteSelectionCommand::handleSpecialCaseBRDelete): Fixed bonehead coding mistake in the
        check for one of the special cases being checked for in this function. The specific case
        intends to check for a selection that is only a <br> after a block ends (as in </div><br>). If it
        sees such markup, it deletes only the <br> and bails. However, this code would run in *any*
        case where a selection ended in a <br> after a block and would not delete any part of the
        selection preceding the <br>. Bad. I have tightened the check to see that only a <br> is
        selected.

        Fixing the bug above was accomplished with an additional call to DOM::Position::downstream. This
        new use of the function exposed this bug:

        <rdar://problem/3907666> Incorrectly coded loop in Position::downstream can lead to infinite loop

        * khtml/xml/dom_position.cpp:
        (DOM::Position::downstream): I am ashamed of my first cut at this. Rewrote the loop so it does
        not have this fatal flaw. It is a much better design as well.

        * layout-tests/editing/deleting/delete-3800834-fix-expected.txt: Changes made this test
        have what I consider to be a better result. Going with it.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8135 268f45cc-cd09-0410-ab3c-d52691b4dbfc