Tweak 'scroll' listener registration in CrScrollableBehavior.

ui/webui/resources/cr_elements/cr_scrollable_behavior.js

Index: ui/webui/resources/cr_elements/cr_scrollable_behavior.js
diff --git a/ui/webui/resources/cr_elements/cr_scrollable_behavior.js b/ui/webui/resources/cr_elements/cr_scrollable_behavior.js
index 407fb396a8ac2e85c545f62ad4ce9b437ce16bc2..362753f91b74638a2ba647db2f6d5f85844200c7 100644
--- a/ui/webui/resources/cr_elements/cr_scrollable_behavior.js
+++ b/ui/webui/resources/cr_elements/cr_scrollable_behavior.js
@@ -36,7 +36,7 @@
 
 /** @polymerBehavior */
 var CrScrollableBehavior = {
-  attached: function() {
+  ready: function() {
     var scrollableElements = this.root.querySelectorAll('[scrollable]');
 
     // Setup the intial scrolling related classes for each scrollable container.
@@ -50,15 +50,6 @@ var CrScrollableBehavior = {
       scrollable.addEventListener('scroll', this.updateScrollEvent_.bind(this));
   },
 
-  detached: function() {
-    // Remove 'scroll' event listeners.
-    var scrollableElements = this.root.querySelectorAll('[scrollable]');
-    for (let scrollable of scrollableElements) {
-      scrollable.removeEventListener(
-          'scroll', this.updateScrollEvent_.bind(this));
-    }
-  },
-
   /**
    * Called any time the contents of a scrollable container may have changed.
    * This ensures that the <iron-list> contents of dynamically sized