manifest.json

{
  "manifest_version":2,
  "name": "Remove Canvas",
  "version": "1",
  "permissions": [ "cookies", "tabs", "http://*/*", "https://*/*", "file:///*/*" ],
  "content_scripts": [
    {
      "matches": ["http://*/*", "https://*/*", "file://*/*"],
      "js": ["removecanvas.js"]
    }
  ]
}