Refused to apply inline style because it violates the following Content Security Policy directive: "default-src 'none'".

Refused to apply inline style because it violates the following Content Security Policy directive: "default-src 'none'". Note that 'style-src' was not explicitly set, so 'default-src' is used as a fallback.

popup.html 修正前

<!DOCTYPE html>
<html>
	<script type="text/javascript" src="popup.js">
	</script>

	<head>
		<meta charset="UTF-8">
		<style>
			p { font-size: 32px;}
		</style>
	</head>
	<body>
		<p>Hello, World!</p>

		<input type="number" value="3" min="1" id="second">
		<input type="button" value="セット" id="start">

	</body>
</html>

popup.html 修正後

<!DOCTYPE html>
<html>
	<script type="text/javascript" src="popup.js">
	</script>

	<head>
		<meta charset="UTF-8">

		<link rel="stylesheet" type="text/css" href="popup.css" />
	</head>
	<body>
		<p>Hello, World!</p>

		<input type="number" value="3" min="1" id="second">
		<input type="button" value="セット" id="start">

	</body>
</html>