system/HTTP/ContentSecurityPolicy.php
public function addFrameAncestor($uri, ?bool $explicitReporting = null)
	{
		$this->addOption($uri, 'frameAncestors', $explicitReporting ?? $this->reportOnly);

		return $this;
	}
public function addFrameAncestor($uri, ?bool $explicitReporting = null)
	{
		$this->addOption($uri, 'frameAncestors', $explicitReporting ?? $this->reportOnly);

		return $this;
	}
Adds a new resource that should allow embedding the resource using
<frame>, <iframe>, <object>, <embed>, or <applet>

@see http://www.w3.org/TR/CSP/#directive-frame-ancestors

@param string|array $uri
@param boolean|null $explicitReporting

@return $this