[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..20cff7ccbdf8ab6ccf0f7063a01a32e7cd7ec8f1 100644
--- a/chrome/browser/resources/settings/controls/settings_idle_render.js
+++ b/chrome/browser/resources/settings/controls/settings_idle_render.js
@@ -46,14 +46,16 @@ Polymer({
 
   /** @private */
   render_: function() {
-    if (!this.ctor)
-      this.templatize(this);
-    var parentNode = this.parentNode;
-    if (parentNode && !this.child_) {
-      var instance = this.stamp({});
-      this.child_ = instance.root.firstElementChild;
-      parentNode.insertBefore(instance.root, this);
-    }
+    // Only initialize once.
+    assert(!this.ctor);
+    cancelIdleCallback(this.idleCallback_);
+
+    // Must have a parent and child in order to add child to parent.
+    assert(this.parentNode && !this.child_);
+    this.templatize(this);
+    var instance = this.stamp({});
+    this.child_ = instance.root.firstElementChild;
+    this.parentNode.insertBefore(instance.root, this);
   },
 
   /**