[MD Bookmarks] Fix offscreen menu button activation.

chrome/browser/resources/md_bookmarks/list.js

Index: chrome/browser/resources/md_bookmarks/list.js
diff --git a/chrome/browser/resources/md_bookmarks/list.js b/chrome/browser/resources/md_bookmarks/list.js
index c14fee3a875d948df19b170085da4ecbf1dce45f..e011bbc77e4d3158d824e53d036d16c76759f28f 100644
--- a/chrome/browser/resources/md_bookmarks/list.js
+++ b/chrome/browser/resources/md_bookmarks/list.js
@@ -46,6 +46,7 @@ Polymer({
 
   listeners: {
     'click': 'deselectItems_',
+    'open-item-menu': 'onOpenItemMenu_',
   },
 
   attached: function() {
@@ -131,6 +132,19 @@ Polymer({
     return this.$.bookmarksCard.modelForElement(el).index;
   },
 
+  /**
+   * @param {Event} e
+   * @private
+   */
+  onOpenItemMenu_: function(e) {
+    var index = this.displayedIds_.indexOf(
+        /** @type {BookmarksItemElement} */ (e.path[0]).itemId);
+    var list = this.$.bookmarksCard;
+    // If the item is not visible, scroll to it before rendering the menu.
+    if (index < list.firstVisibleIndex || index > list.lastVisibleIndex)
+      list.scrollToIndex(index);
+  },
+
   /**
    * @param {KeyboardEvent} e
    * @private