Replace the TED player with the equivalent YouTube video.

manifest.json

{
  "name": "TED YouTube embed",
  "version": "1.0",
  "description": "Replace the TED player with the equivalent YouTube video.",
  "content_scripts": [
    {
      "matches": ["*://www.ted.com/talks/*"],
      "js": ["replace.js"],
      "run_at": "document_end"
    }
  ],
  "manifest_version": 2
}

replace.js

// https://developers.google.com/youtube/v3/docs/search/list

var video = document.getElementById("player-hero");
var key = "AIzaSyD4v-XiK6_XDCDiMccTO6_Y1hNn03ft9Gc";

if (video) {
  function callback() {
    console.log(this.responseURL);
    console.log(this);
    var data = JSON.parse(this.responseText);
    console.log(data);
    if (data.error) {
      console.log(data.error.message);
      return;
    }
    if (!data.items || !data.items[0] || !data.items[0].id.videoId) {
      console.log("Can't find video.");
      return;
    }
    var item = data.items[0];
    var video_id = item.id.videoId;
    console.log(`https://www.youtube.com/watch?v=${video_id}`);
    video.innerHTML = `<iframe width="853" height="480" src="https://www.youtube.com/embed/${video_id}?rel=0" frameborder="0" allowfullscreen style="display:block; margin:0 auto;"></iframe>`;
  }

  // Glenn Greenwald: Why privacy matters | TED Talk | TED.com
  var q = document.title.split("|")[0].trim();
  console.log(q);

  var url = `https://www.googleapis.com/youtube/v3/search?key=${key}&part=id&q=${q}`;
  var xhr = new XMLHttpRequest();
  xhr.addEventListener("load", callback);
  xhr.open("GET", url);
  xhr.send();
}