findObjectOfClass.js

var objs = new Set(); // we'll store the object references in this array

function walkTheObject(obj) {
  var requiredClass = "MediaStreamTrack";
  var keys = {};
  try {
    keys = Object.keys(obj); // get all own property names of the object
  } catch {}
  keys.forEach(function (key) {
    try {
      var value = obj[key]; // get property value

      // if the property value is an object...
      if (value && typeof value === "object") {
        // if we don't have this reference...
        if (!objs.has(value)) {
          objs.add(value); // store the reference
          if(value.__proto__ && 
             value.__proto__.constructor && 
             value.__proto__.constructor.name && 
            value.__proto__.constructor.name === requiredClass)
          {
            console.log("Found!");
          }
          walkTheObject(value); // traverse all its own properties
        }
      }
    } catch {}
  });
}

new Promise(_ => {
  walkTheObject(this);
  console.log("Done!");
});