Update references to the extension messaging APIs to point to the "runtime"

chrome/common/extensions/api/tts.json

 // 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.
 
 [
   {
     "namespace": "tts",
     "types": [
       {
         "id": "TtsEvent",
@@ skipping 151 matching lines @@
                     "description": "The update event from the text-to-speech engine indicating the status of this utterance."
                   }
                 ]
               }
             }
           },
           {
             "type": "function",
             "name": "callback",
             "optional": true,
-            "description": "Called right away, before speech finishes. Check chrome.extension.lastError to make sure there were no errors. Use options.onEvent to get more detailed feedback.",
+            "description": "Called right away, before speech finishes. Check chrome.runtime.lastError to make sure there were no errors. Use options.onEvent to get more detailed feedback.",
             "parameters": []
           }
         ]
       },
       {
         "name": "stop",
         "type": "function",
         "description": "Stops any current speech.",
         "parameters": []
       },
@@ skipping 47 matching lines @@
             "name": "event",
             "$ref": "TtsEvent",
             "description": "The event from the text-to-speech engine indicating the status of this utterance."
           }
         ],
         "description": "Used to pass events back to the function calling speak()."
       }
     ]
   }
 ]