public function updateTabIndex() {
		$disabled = $this->isDisabled();
		if ( $this->tabIndex !== null ) {
			$this->tabIndexed->setAttributes( [
				// Do not index over disabled elements
				'tabindex' => $disabled ? -1 : $this->tabIndex,
				// ChromeVox and NVDA do not seem to inherit this from parent elements
				'aria-disabled' => ( $disabled ? 'true' : 'false' )
			] );
		} else {
			$this->tabIndexed->removeAttributes( [ 'tabindex', 'aria-disabled' ] );
		}
		return $this;
	}