Rename Position::container to m_anchorNode and make it private
        https://bugs.webkit.org/show_bug.cgi?id=24760

        More code cleanup for Position.

        Change all uses of m_container to node()
        Eventually most uses of node() should change to anchorNode() to designate
        that it's the node the Position is anchored to, but not necessarily the
        container of the position (it could be the before/after neighbor).

        Remove any code which sets m_container, and change it to use a new
        Position::moveToPosition function which takes a node and offset.
        It never makes sense to change the node and leave the offset.

        * dom/Position.h:
        (WebCore::Position::Position):
        (WebCore::Position::clear):
        (WebCore::Position::anchorNode):
        (WebCore::Position::node):
        (WebCore::Position::moveToPosition):
        (WebCore::Position::moveToOffset):
        (WebCore::Position::isNull):
        (WebCore::Position::isNotNull):
        (WebCore::operator==):
        * dom/Range.cpp:
        (WebCore::Range::create):
        (WebCore::Range::compareBoundaryPoints):
        * dom/RangeBoundaryPoint.h:
        (WebCore::RangeBoundaryPoint::container):
        (WebCore::RangeBoundaryPoint::set):
        (WebCore::RangeBoundaryPoint::setOffset):
        (WebCore::RangeBoundaryPoint::setToChild):
        (WebCore::RangeBoundaryPoint::setToStart):
        (WebCore::RangeBoundaryPoint::setToEnd):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@41933 268f45cc-cd09-0410-ab3c-d52691b4dbfc