Examine source code of Flip images

{
  "description": "Flips images horizontally and/or vertically",
  "manifest_version": 2,
  "name": "Flip images",
  "version": "1.0.1",
  "icons": {
    "48": "icons/hv_48.png",
    "96": "icons/hv_96.png"
  },
  "permissions": [],
  "browser_action": {
    "default_icon": {
      "32": "icons/32.png"
    },
    "default_title": "Flipper"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "flip.js"
      ]
    }
  ]
}