Reviewed by Eric Seidel.

        pushDownTextDecorationStyleAroundNode needs clean up
        https://bugs.webkit.org/show_bug.cgi?id=27556

        Cleaned up. pushDownTextDecorationStyleAroundNode traverses tree vertically from highestAncestor to targetNode
        While traversing, it will apply the specified style to all nodes but targetNode.
        i.e. the style is applies to all ancestor nodes and their siblings of targetNode.

        * editing/ApplyStyleCommand.cpp:
        (WebCore::ApplyStyleCommand::pushDownTextDecorationStyleAroundNode): Cleaned up and added comments
        * editing/ApplyStyleCommand.h: Updated prototype



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@46238 268f45cc-cd09-0410-ab3c-d52691b4dbfc