The bit of code in ember.js that is pausing for a good second or so.

ember-flush.js

RunLoop.prototype = {
  /**
    @method end
  */
  end: function() {
    this.flush();
  },
// …

ember-try-finally.js

Ember.tryFinally = function(tryable, finalizer, binding) {
  var result, finalResult;

  binding = binding || this;

  try {
    result = tryable.call(binding);
  } finally {
    finalResult = finalizer.call(binding); // THIS LINE PAUSES, SOMETIMES
  }

  return (finalResult === undefined) ? result : finalResult;
};