Enable runtime switching between ChromeVox and ChromeVox next via command line.

chrome/browser/resources/chromeos/chromevox/cvox2/background/background.extjs

 // 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.
 
 // Include test fixture.
-GEN_INCLUDE(['../../../chromevox/testing/chromevox_e2e_test_base.js']);
+GEN_INCLUDE(['../../testing/chromevox_e2e_test_base.js']);
 
 /**
  * Test fixture for cvox2.Background.
  * @constructor
  * @extends {ChromeVoxE2ETest}
  */
 function BackgroundTest() {}
 
 BackgroundTest.prototype = {
   __proto__: ChromeVoxE2ETest.prototype,
 
+  // This method is called without a |this| instance bound.
+  /** @override */
+  testGenCppIncludes: function() {
+    ChromeVoxE2ETest.prototype.testGenCppIncludes.call(this);
+    GEN('#include "base/command_line.h"');
+    GEN('#include "chromeos/chromeos_switches.h"');
+  },
+
+  // This method is called without a |this| instance bound.
+  /** @override */
+  testGenPreamble: function() {
+    GEN_BLOCK(function() {/*!
+      CommandLine* command_line = CommandLine::ForCurrentProcess();
+      command_line->AppendSwitch(chromeos::switches::kEnableChromeVoxNext);
+    */});
+    ChromeVoxE2ETest.prototype.testGenPreamble.call(this);
+  },
+
   /** @override */
   setUp: function() {
     this.mockTts = new MockTts();
     cvox.ChromeVox.tts = this.mockTts;
   }
 };
 
 /**
  * Mock tts class.
  * @constructor
@@ skipping 57 matching lines @@
     testButton.addEventListener(chrome.automation.EventType.focus,
         function(e) {
           var result =
               cvox.ChromeVox.tts.checkIfSubstringWasSpoken('Status tray');
           testDone([result, '']);
         },
         true);
     testButton.focus();
   });
 });