[MD settings] handle being detached on cr-lazy-render and settings-idle-render

chrome/browser/resources/settings/controls/settings_idle_render.js

Index: chrome/browser/resources/settings/controls/settings_idle_render.js
diff --git a/chrome/browser/resources/settings/controls/settings_idle_render.js b/chrome/browser/resources/settings/controls/settings_idle_render.js
index 8e224c9e5414b54437e08f556a7411fdbb2a9868..44fc1d3f990090f91d1908c5b654c3cf83faf05e 100644
--- a/chrome/browser/resources/settings/controls/settings_idle_render.js
+++ b/chrome/browser/resources/settings/controls/settings_idle_render.js
@@ -30,6 +30,7 @@ Polymer({
 
   /** @override */
   detached: function() {
+    this.child_ = null;

[Dan Beam, 2017/02/11 23:01:35]

but wait, does this mean it could get double-rendered?

can we maybe rename child_ to something less cryptic?

[tsergeant, 2017/02/15 06:31:39]

Yeah, if you detach the settings-idle-render, its internal state is reset to
having no child, but that child can still be rendered and attached to the DOM
tree.

dom-if handles this by ensuring that the rendered template instance is destroyed
when the template is detached:

https://github.com/Polymer/polymer/blob/6fc567fbf4e69ab1be2623212d5254eb38515...

     // No-op if callback already fired.
     cancelIdleCallback(this.idleCallback_);
   },