Need iron-resize to be notified earlier in neon-animated-pages before the animation starts

[omarbelkhodja]

Description

I'm using multiple pages, each of them has an app-layout-header. I'am animating the transition between the different pages.The app-layout-header needs to resize, each time a new page is visible.

Expected outcome

A correct display of each page.

Actual outcome

The content of the pages is wrong until the new page finishes the transition, because the app-layout-header component is using some header.heightOffset, which is zero, when page is not visible (display: none).
The resize event should be notified as soon as "display: none" is removed.

I added the last line in the following code inside neon-animated-pages, to fix my problem :

_onIronSelect: function(event) {
   ...
    // display the selectedPage during the transition.
   selectedPage.classList.add('neon-animating');
   // Resize the selected page
   this.async(this._notifyPageResize);

[mgibas]

Notifying page before animation as in @omarbelkhodja example fixes the issue.

Related issue: PolymerElements/app-layout#280