To skip Ads in Youtube.

manifest.json

{
  "manifest_version": 2,
  "name": "skipYoutubeAds",
  "version": "0.0.1",

  "description": "To skip Ads in Youtube.",

  "content_scripts": [
    {
      "matches": ["https://www.youtube.com/watch*","http://www.youtube.com/watch*"],
      "js": ["skipYoutubeAds.js"],
      "run_at": "document_start"
    }
  ]
}

skipYoutubeAds.js

(function(){
var $ = function(selector, parentElement) {
  return (parentElement || document).querySelector(selector);
};

window.addEventListener('load', function(){
  setTimeout(function hiddenAds(){
    var video = $('video');
    if ($('.ad-container')) $('.ad-container').style.display = "none";
    var video_id;
    location.search.substr(1).split('&').forEach(function(query) {
      if (query.match('^v=')) video_id = query.split('=')[1];
    });
    if (video.readyState === 4 && video_id !== video.getAttribute('data-youtube-id')) {
      video.currentTime = video.duration;
    }
    setTimeout(hiddenAds, 100);
  }, 100);
});
})();