[MD Bookmarks] Convert bookmark list to iron-list.

chrome/browser/resources/md_bookmarks/item.js

Index: chrome/browser/resources/md_bookmarks/item.js
diff --git a/chrome/browser/resources/md_bookmarks/item.js b/chrome/browser/resources/md_bookmarks/item.js
index c0be4847f2849e7449f9dea0103cdba3555ad008..1b851c4c619bc28746ee1d00820c9fd0e9509ac9 100644
--- a/chrome/browser/resources/md_bookmarks/item.js
+++ b/chrome/browser/resources/md_bookmarks/item.js
@@ -15,6 +15,8 @@ Polymer({
       observer: 'onItemIdChanged_',
     },
 
+    ironListTabIndex: String,
+
     /** @private {BookmarkNode} */
     item_: {
       type: Object,
@@ -27,6 +29,12 @@ Polymer({
       reflectToAttribute: true,
     },
 
+    /** @private */
+    mouseFocus_: {
+      type: Boolean,
+      reflectToAttribute: true,
+    },
+
     /** @private */
     isFolder_: Boolean,
   },
@@ -36,6 +44,8 @@ Polymer({
   ],
 
   listeners: {
+    'mousedown': 'onMousedown_',
+    'blur': 'onBlur_',
     'click': 'onClick_',
     'dblclick': 'onDblClick_',
     'contextmenu': 'onContextMenu_',
@@ -108,6 +118,20 @@ Polymer({
     this.isFolder_ = !this.item_.url;
   },
 
+  /**
+   * @private
+   */
+  onMousedown_: function() {
+    this.mouseFocus_ = true;

[tsergeant, 2017/05/15 01:14:27]

I think this is going to be buggy. For example, I can mousedown on an item, drag
my mouse away from it and then mouseup on a different item. This will apply
mouseFocus_ without ever focusing the item, and if I then keyboard focus the
item, no outline will show up.

You could check the focus-ring polyfill to see the approach it takes (kind of
the opposite).

[calamity, 2017/05/16 02:54:15]

Added the focus handler to the button as discussed.

+  },
+
+  /**
+   * @private
+   */
+  onBlur_: function() {
+    this.mouseFocus_ = false;
+  },
+
   /**
    * @param {Event} e
    * @private