GoogleHandler::getFileSizeInternal

private function getFileSizeInternal($downloadUrl)
{
	$accessToken = $this->getAccessToken();
	$http = new HttpClient(array(
		'socketTimeout' => 10,
		'streamTimeout' => 30,
		'version' => HttpClient::HTTP_1_1,
	));
	$http->setHeader('Authorization', "Bearer {$accessToken}");

	if($http->query('HEAD', $downloadUrl) === false)
	{
		$errorString = implode('; ', array_keys($http->getError()));
		$this->errorCollection[] = new Error(
			$errorString, self::ERROR_HTTP_GET_METADATA
		);
		return null;
	}

	if(!$this->checkHttpResponse($http))
	{
		return null;
	}

	return $http->getHeaders()->get('Content-Length');
}