class WP_Customize_Textarea_Control extends WP_Customize_Control {
        public $type = 'textarea';

        public function render_content() {
            ?>
            <label>
                <span class="customize-control-title"><?php echo esc_html( $this->label ); ?></span>
            <textarea rows="5" style="width:100%;" name="<?php echo esc_attr( $name ); ?>" <?php $this->link(); ?>><?php echo esc_attr( $this->value() ); ?></textarea>
            </label>
            <?php
        }
    }