Refused to execute inline script because it violates the following Content Security Policy directive: "script-src 'self' chrome-extension-resource:".

Manifest.json

{
	// Required
	"name": "Sample Extension",
	"version": "0.2",
	"manifest_version": 2,

	"background": { "page": "background.html"},

	"browser_action": {
		"default_icon": "icon.png",
		"default_popup": "popup.html"
	}
}

Chrome Extensionのmanifestバージョンを上げる(1から2へ) - ike-daiの日記

chrome extension で manifest version 2にするとインラインスクリプトが使えないとのことで。