Update TTS extension API docs to reflect latest changes. Note that this

chrome/test/data/extensions/api_test/tts/word_callbacks/test.js

 // Copyright (c) 2011 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.
 
 // TTS api test for Chrome on ChromeOS.
 // browser_tests.exe --gtest_filter="TtsApiTest.*"
 
 chrome.test.runTests([
   function testWordCallbacks() {
     var callbacks = 0;
     chrome.experimental.tts.speak(
         'one two three',
         {
-         'onevent': function(event) {
+         'onEvent': function(event) {
            callbacks++;
            switch(callbacks) {
            case 1:
              chrome.test.assertEq('word', event.type);
              chrome.test.assertEq(0, event.charIndex);
              break;
            case 2:
              chrome.test.assertEq('word', event.type);
              chrome.test.assertEq(4, event.charIndex);
              break;
            case 3:
              chrome.test.assertEq('word', event.type);
              chrome.test.assertEq(8, event.charIndex);
              break;
            case 4:
              chrome.test.assertEq('end', event.type);
              chrome.test.assertEq(13, event.charIndex);
              chrome.test.succeed();
              break;
            default:
              chrome.test.fail();
            }
          }
         });
   }
 ]);