New Twiddle

components.ember-dropdown-trigger.js

import Ember from 'ember';

export default Ember.Component.extend({
  click(event) {
    this.get('onClick')(event);
  }
});

components.ember-dropdown.js

import Ember from 'ember';

export default Ember.Component.extend({
  show: false,
  toggle() {
    this.toggleProperty('show')
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.content {
  border: 1px solid red;
}

templates.application.hbs

{{#ember-dropdown as |dropdown|}}
	{{dropdown.trigger tagName="button" label="Toggle"}}  
	{{#dropdown.content}}
    <ul>
      <li>One</li>
      <li>Two</li>
      <li>Three</li>    
    </ul>
  {{/dropdown.content}}
{{/ember-dropdown}}

templates.components.ember-dropdown-content.hbs

{{#if show}}
  <div class="content">
  	{{yield}}
  </div>
{{/if}}

templates.components.ember-dropdown-trigger.hbs

{{#if hasBlock}}
	{{yield}}
{{else}}
	{{label}}
{{/if}}

templates.components.ember-dropdown.hbs

{{yield (hash
	trigger=(component "ember-dropdown-trigger" onClick=(action toggle))
  content=(component "ember-dropdown-content" show=show)
)}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}