Handle cases when app-drawer is appended later

[keanulee]

Might fix #273

[keanulee]

Actually, this will cause more work if app-drawer is already attached during init - need to revisit

[frankiefu]

We might want to handle for the case when app-drawer is upgraded (e.g. lazy import) later.

[keanulee]

@frankiefu Does lazy import mean the custom attached callback is run after the element is customized? If so, then it should Just Work^TM.

[frankiefu]

Yeah. Just tried out one of the app-drawer-layout demo and noticed couple things:

• this.drawer may return <app-drawer> but hasn't been upgraded yet, so at load time it tries to call this.drawer.getWidth() and that generates an error.
• because of the error above, resetLayout didn't setup the layout correctly.

[frankiefu]

LGTM

[milky2028]

Hello! I'm currently having this issue using Polymer 2, though it says here it's been resolved. I updated my dependencies, but the issue persists.

[milky2028]

This is resulting in the drawer not resetting, so things like

// Close a non-persistent drawer when the page & route are changed.
        if (!this.$.drawer.persistent) {
          this.$.drawer.close();
        } 

don't work properly. The drawer stays open on page changes.