http://bugs.webkit.org/show_bug.cgi?id=15922
        Implement more of Mozilla Selection API

        Tests: editing/selection/containsNode.html
               editing/selection/deleteFromDocument.html
               editing/selection/extend.html
               editing/selection/selectAllChildren.html

        * editing/SelectionController.cpp:
        (WebCore::SelectionController::deleteFromDocument):
        (WebCore::SelectionController::containsNode):
        (WebCore::SelectionController::selectAllChildren):
        (WebCore::SelectionController::extend):
        * editing/SelectionController.h:
        Added deleteFromDocument(), containsNode(), and selectAllChildren(). Reimplemented extend(),
        which existed, but didn't match Firefox behavior and wasn't exposed via bindings.
        Removed a comment mentioning removeRange(), as this method makes no sense without multiple
        selection range support.

        * page/DOMSelection.cpp:
        (WebCore::DOMSelection::extend):
        (WebCore::DOMSelection::deleteFromDocument):
        (WebCore::DOMSelection::containsNode):
        (WebCore::DOMSelection::selectAllChildren):
        * page/DOMSelection.h:
        * page/DOMSelection.idl:
        Exposed the new methods.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@27666 268f45cc-cd09-0410-ab3c-d52691b4dbfc