MD History: Prevent focus ring when clicking on 'Clear Browsing Data'

chrome/browser/resources/md_history/side_bar.js

Index: chrome/browser/resources/md_history/side_bar.js
diff --git a/chrome/browser/resources/md_history/side_bar.js b/chrome/browser/resources/md_history/side_bar.js
index cfc0b9434896c861e74240b9263250353c4bac8f..34697cf819d11079c3c1476889d450dd2d6f04df 100644
--- a/chrome/browser/resources/md_history/side_bar.js
+++ b/chrome/browser/resources/md_history/side_bar.js
@@ -55,11 +55,11 @@ Polymer({
   },
 
   /**
-   * @return {number}
+   * @return {string}
    * @private
    */
   computeClearBrowsingDataTabIndex_: function() {
-    return this.guestSession_ ? -1 : 0;
+    return this.guestSession_ ? '-1' : '';
   },
 
   /**