the demos don't work in Chrome and Opera

[lext-7]

I downloaded the source code from polymer-project.
But the demo.html of papar-dropdown-menu didn't work in Chrome and Opera, but it worked in IE and Firefox.

[lext-7]

I came to see the online demo website of polymer, I tried to figure out why their codes worked well. Finally I found a lit bit difference.
My file 'core-animation/web-animation.html' :

<script src="../web-animations-js/web-animations-next-lite.min.js"></script>

The one online:

<link rel="import" href="../web-animations-next/web-animations.html">

After I changed it, it worked as I expected.

Great.