MD Settings: fix focus-row-behavior allowing invisible focus on rows.

chrome/browser/resources/settings/focus_row_behavior.js

Index: chrome/browser/resources/settings/focus_row_behavior.js
diff --git a/chrome/browser/resources/settings/focus_row_behavior.js b/chrome/browser/resources/settings/focus_row_behavior.js
index 286c4eb65d62b9064f01002b28c7ce707f3d3e58..6a0b86614e0a59db5ab5c91881b070c4e9240f13 100644
--- a/chrome/browser/resources/settings/focus_row_behavior.js
+++ b/chrome/browser/resources/settings/focus_row_behavior.js
@@ -20,6 +20,7 @@ FocusRowDelegate.prototype = {
    */
   onFocus: function(row, e) {

[hcarmona, 2017/06/08 18:57:50]

When does this |onFocus| get called?

[scottchen, 2017/06/08 22:55:35]

When a control element (i,e, [focus-row-control]) within the list gets focused.

[hcarmona, 2017/06/08 23:21:31]

Sounds good. Let's add a short comment to both focus functions to remove
ambiguity about when they are called.

[scottchen, 2017/06/09 00:06:00]

Done.

     this.listItem_.lastFocused = e.path[0];
+    this.listItem_.tabIndex = -1;
   },
 
   /**