core-scroll-header-panel won't hide navigation bar on Android (stable and beta)

[gulbrillo]

This is not a duplicate of googlearchive/core-scroll-header-panel#4 but related to googlearchive/core-scroll-header-panel#1 which is not fixed by Chrome beta for Android. :(
(but: everything is much smoother in Chrome beta - awesome work!)

1. Open
   http://www.polymer-project.org/components/core-scroll-header-panel/demo.html
   on Chrome for Android.
2. Scroll down.
3. Issue: The Chrome navigation bar will not hide automatically as it does on any other website.

I guess it has something to do with the header not being inside the scrollable element, so it might be fixed by fixing googlearchive/core-scroll-header-panel#1 - but I'm not sure about that.

[tjsavage]

auto-moving this issue to googlearchive/core-scroll-header-panel#15 and closing this one