Prevent focus from leaving Print Preview overlay controls.

chrome/browser/resources/print_preview/print_preview_focus_manager.js

+// Copyright 2014 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.
+
+cr.define('print_preview', function() {
+  'use strict';
+
+  /**
+   * FocusManager implementation specialized for Print Preview, which ensures
+   * that Print Preview itself does not receive focus when an overlay is shown.
+   * @constructor
+   */
+  function PrintPreviewFocusManager() {
+  };
+
+  cr.addSingletonGetter(PrintPreviewFocusManager);
+
+  PrintPreviewFocusManager.prototype = {
+    __proto__: cr.ui.FocusManager.prototype,
+
+    /** @override */
+    getFocusParent: function() {
+      return document.querySelector('.overlay:not([hidden])') ||
+          document.body;
+    }
+  };
+
+  // Export
+  return {
+    PrintPreviewFocusManager: PrintPreviewFocusManager
+  };
+});