{
  "name": "Github - Date of creation",
  "version": "1.0.0",
  "manifest_version": 2,
  "description": "Display a date of creation of a repository hosted on Github",
  "homepage_url": "https://github.com/lvarayut/github-date-of-creation",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "author": "Varayut Lerdkanlayanawat",
  "page_action": {
    "default_icon": "icons/icon19.png",
    "default_title": "Github - Date of creation"
  },
  "permissions": [
    "http://github.com/*",
    "https://github.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
				"http://github.com/*",
				"https://github.com/*"
      ],
      "js": [
        "src/vendors/moment.min.js",
        "src/inject/inject.js"
      ]
    }
  ]
}

{
  "name": "Github - Date of creation",
  "version": "1.0.0",
  "manifest_version": 2,
  "description": "Display a date of creation of a repository hosted on Github",
  "homepage_url": "https://github.com/lvarayut/github-date-of-creation",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "author": "Varayut Lerdkanlayanawat",
  "browser_action": {
    "default_icon": "icons/icon19.png"
  },
  "permissions": [
    "http://github.com/*",
    "https://github.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
				"http://github.com/*",
				"https://github.com/*"
      ],
      "js": [
        "src/vendors/moment.min.js",
        "src/inject/inject.js"
      ]
    }
  ]
}

Use browser_action instead of page_action
Use browser_action instead of page_action
