Add setSelection function to automation API.

chrome/test/data/extensions/api_test/automation/tests/desktop/actions.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.
 
-function listenOnce(node, eventType, callback, capture) {
-  var innerCallback = function() {
-    node.removeEventListener(eventType, innerCallback, capture);
-    callback();
-  };
-  node.addEventListener(eventType, innerCallback, capture);
-};
-
 var allTests = [
   function testDoDefault() {
     var firstTextField = findAutomationNode(rootNode,
         function(node) {
           return node.role == 'textField';
         });
     assertTrue(!!firstTextField);
     listenOnce(firstTextField, EventType.focus, function(e) {
       chrome.test.succeed();
     }, true);
@@ skipping 24 matching lines @@
   function testContextMenu() {
     var addressBar = rootNode.find({role: 'textField'});
     listenOnce(rootNode, EventType.menuStart, function(e) {
       addressBar.showContextMenu();
       chrome.test.succeed();
     }, true);
     addressBar.showContextMenu();
   }
 ];
 
-setupAndRunTests(allTests);
+setUpAndRunTests(allTests);