Emulator.prototype.start = function() {
  ...
  var handleGameData = this.handleGameData.bind(this),
      handleGameFiles = this.handleGameFiles.bind(this),
      init = this.init.bind(this),
      run = this.run.bind(this);

  loading.then(handleGameData)
         .then(handleGameFiles)
         .then(init)
         .then(run);
   ...
}
Emulator.prototype.handleGameData = function(gamedata) {
  ...
}
Emulator.prototype.handleGameFiles = function(files) {
  ...
}
Emulator.prototype.init = function() {
  ...
}
Emulator.prototype.run = function() {
  ...
}