Play it once, Sam

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "version": "0.2",
  "name": "Play it once, Sam",
  "description": "...for old times' sake. Play entries of YouTube's watch later list without advancing to next title.",
  "icons": {
    "128": "icon_mode0_128.png"
  },
  "page_action": {
    "default_icon": {
      "19": "icon_mode0_19.png",
      "38": "icon_mode0_38.png"
    },
    "default_popup": "options.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "storage",
    "tabs",
    "webRequest",
    "webRequestBlocking",
    "*://www.youtube.com/"
  ]
}