v3 preview throws exceptions

[TitanNano]

Description

There seem to be some conversion issues in the 3.0.0 preview 10.
The following errors are thrown when clicking the trigger element:

Steps to reproduce

Use a snippet from the demo:

      <paper-menu-button>
        <paper-icon-button icon="menu" slot="dropdown-trigger" alt="menu"></paper-icon-button>
        <paper-listbox slot="dropdown-content">
          <paper-item>alpha</paper-item>
          <paper-item>beta</paper-item>
          <paper-item>gamma</paper-item>
          <paper-item>delta</paper-item>
          <paper-item>epsilon</paper-item>
        </paper-listbox>
      </paper-menu-button>

Browsers Affected

• Chrome
• Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10

[ratracegrad]

I had the exact same error message (but in Polymer 2) using the exact same code snippet from the demo. I was able to resolve this problem by including the web animations polyfill. Once I imported that on my page this error went away.