Fix some uses of global variables in transient pages.

chrome/renderer/resources/extensions/tts_custom_bindings.js

 // Copyright (c) 2012 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.
 
 // Custom bindings for the tts API.
 
 var ttsNatives = requireNative('tts');
 var GetNextTTSEventId = ttsNatives.GetNextTTSEventId;
 
 var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
 var sendRequest = require('sendRequest').sendRequest;
+var lazyBG = requireNative('lazy_background_page');
 
 chromeHidden.registerCustomHook('tts', function(api) {
   var apiFunctions = api.apiFunctions;
 
   chromeHidden.tts = {};
   chromeHidden.tts.handlers = {};
   chrome.tts.onEvent.addListener(function(event) {
     var eventHandler = chromeHidden.tts.handlers[event.srcId];
     if (eventHandler) {
       eventHandler({
                      type: event.type,
                      charIndex: event.charIndex,
                      errorMessage: event.errorMessage
                    });
       if (event.isFinalEvent) {
         delete chromeHidden.tts.handlers[event.srcId];
+        // Balanced in 'speak' handler.
+        lazyBG.DecrementKeepaliveCount();
       }
     }
   });
 
   apiFunctions.setHandleRequest('speak', function() {
     var args = arguments;
     if (args.length > 1 && args[1] && args[1].onEvent) {
       var id = GetNextTTSEventId();
       args[1].srcId = id;
       chromeHidden.tts.handlers[id] = args[1].onEvent;
+      // Keep the page alive until the event finishes.
+      // Balanced in eventHandler.
+      lazyBG.IncrementKeepaliveCount();
     }
     sendRequest(this.name, args, this.definition.parameters);
     return id;
   });
 });