with_output_buffer

# File actionpack/lib/action_view/helpers/capture_helper.rb, line 181
      def with_output_buffer(buf = nil) #:nodoc:
        unless buf
          buf = ActionView::OutputBuffer.new
          buf.force_encoding(output_buffer.encoding) if output_buffer.respond_to?(:encoding) && buf.respond_to?(:force_encoding)
        end
        self.output_buffer, old_buffer = buf, output_buffer
        yield
        output_buffer
      ensure
        self.output_buffer = old_buffer
      end