Reviewed by john

    Reviewed by john

        <rdar://problem/4854869>
        Inserting a new line in a contenteditable=true SPAN whose parent is a DIV asserts

        * editing/htmlediting.cpp:
        (WebCore::enclosingBlock): Use enclosingNodeWithType to prevent escape
        from editable content.
        * editing/markup.cpp:
        (WebCore::createMarkup): A null commonAncestorBlock will happen
        if commonAncestor is inside an inline editable root that doesn't
        contain any blocks.  Removed an early return for this case: the
        code below the early return can and must handle it.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@18051 268f45cc-cd09-0410-ab3c-d52691b4dbfc