Keep track of accessibility focus across windows.

chrome/test/data/extensions/api_test/automation/tests/desktop/focus_views.js

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var allTests = [
+  function testFocusLocationBar() {
+    var firstFocusableNode = findAutomationNode(rootNode,
+        function(node) {
+          return node.role == 'textField' && node.state.focusable;
+        });
+
+    assertTrue(!!firstFocusableNode);
+    listenOnce(firstFocusableNode, EventType.focus, function(e) {
+      chrome.test.succeed();
+    }, true);
+    firstFocusableNode.focus();
+  }
+];
+
+setUpAndRunTests(allTests);