MD Settings: Ensure iron-lists are populated and sized correctly.

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..491ec506cff0049d139387c7614ca9bfc4138f9f 100644
--- a/ui/webui/resources/cr_elements/cr_scrollable_behavior.js
+++ b/ui/webui/resources/cr_elements/cr_scrollable_behavior.js
@@ -65,23 +65,11 @@ var CrScrollableBehavior = {
    * containers are resized correctly.
    */
   updateScrollableContents() {
-    let nodeList = this.root.querySelectorAll('[scrollable] iron-list');
-    // Use setTimeout to avoid initial render / sizing issues.
-    let intervalId = setInterval(function() {
-      let unreadyNodes = [];
-      for (let node of nodeList) {
-        if (node.parentNode.scrollHeight == 0) {
-          unreadyNodes.push(node);
-          continue;
-        }
-        let ironList = /** @type {!IronListElement} */ (node);
-        ironList.notifyResize();
-      }
-      if (unreadyNodes.length == 0)
-        clearInterval(intervalId);
-      else
-        nodeList = unreadyNodes;
-    }, 10);
+    this.async(function() {
+      let lists = this.root.querySelectorAll('[scrollable] iron-list');
+      for (list of lists)
+        list.fire('iron-resize');
+    }.bind(this));
   },
 
   /**