Disables the ability to tab to navigation items when an overlay is displayed.

chrome/browser/resources/uber/uber.js

Index: chrome/browser/resources/uber/uber.js
diff --git a/chrome/browser/resources/uber/uber.js b/chrome/browser/resources/uber/uber.js
index c46a82137592b2e0859c425b8ff24cd550aa17b9..02cd749e4b4bf1f045d27918084f07d848d315df 100644
--- a/chrome/browser/resources/uber/uber.js
+++ b/chrome/browser/resources/uber/uber.js
@@ -138,6 +138,10 @@ cr.define('uber', function() {
       showPage(e.data.params.pageId, HISTORY_STATE_OPTION.PUSH);
     else if (e.data.method === 'navigationControlsLoaded')
       onNavigationControlsLoaded();
+    else if (e.data.method === 'enableNavigationItemTabbing')
+      setNavigationItemTabbing(true);
+    else if (e.data.method === 'disableNavigationItemTabbing')
+      setNavigationItemTabbing(false);
     else if (e.data.method === 'adjustToScroll')
       adjustToScroll(e.data.params);
     else if (e.data.method === 'mouseWheel')
@@ -330,6 +334,18 @@ cr.define('uber', function() {
     uber.invokeMethodOnWindow(iframe.contentWindow, 'mouseWheel', params);
   }
 
+  /**
+   * Enables or disables the ability to tab to the navigation items.
+   * @param {boolean} enabled If true, enables tabbing; if false, disables it.
+   */
+  function setNavigationItemTabbing(enabled) {
+    navFrame.firstChild.tabIndex = enabled ? 0 : -1;
+    if (enabled)
+      navFrame.firstChild.removeAttribute('aria-hidden');
+    else
+      navFrame.firstChild.setAttribute('aria-hidden', true);
+  }
+
   return {
     onLoad: onLoad,
     onPopHistoryState: onPopHistoryState