restore_state (PDF::Writer)

          # File lib/pdf/writer.rb, line 1784
    1784:   def restore_state
    1785:     unless @state_stack.empty?
    1786:       state = @state_stack.pop
    1787:       @current_fill_color         = state.fill_color
    1788:       @current_stroke_color       = state.stroke_color
    1789:       @current_text_render_style  = state.text_render_style
    1790:       @current_stroke_style       = state.stroke_style
    1791:       stroke_style!
    1792:     end
    1793:     add_content("\nQ")
    1794:   end