Clean up some old TODOs

chrome/renderer/renderer_webidbcursor_impl.cc

 // Copyright (c) 2010 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 "chrome/renderer/renderer_webidbcursor_impl.h"
 
 #include "chrome/common/indexed_db_messages.h"
 #include "chrome/renderer/indexed_db_dispatcher.h"
 #include "chrome/renderer/render_thread.h"
 
 using WebKit::WebExceptionCode;
 using WebKit::WebIDBCallbacks;
 using WebKit::WebIDBKey;
 using WebKit::WebSerializedScriptValue;
 
 RendererWebIDBCursorImpl::RendererWebIDBCursorImpl(int32 idb_cursor_id)
     : idb_cursor_id_(idb_cursor_id) {
 }
 
 RendererWebIDBCursorImpl::~RendererWebIDBCursorImpl() {
+  // It's not possible for there to be pending callbacks that address this
+  // object since inside WebKit, they hold a reference to the object wich owns
+  // this object. But, if that ever changed, then we'd need to invalidate
+  // any such pointers.
   RenderThread::current()->Send(new IndexedDBHostMsg_CursorDestroyed(
       idb_cursor_id_));
 }
 
 unsigned short RendererWebIDBCursorImpl::direction() const {
   int direction;
   RenderThread::current()->Send(
       new IndexedDBHostMsg_CursorDirection(idb_cursor_id_, &direction));
   return direction;
 }
@@ skipping 36 matching lines @@
   dispatcher->RequestIDBCursorContinue(IndexedDBKey(key), callbacks,
                                        idb_cursor_id_, &ec);
 }
 
 void RendererWebIDBCursorImpl::remove(WebIDBCallbacks* callbacks,
                                       WebExceptionCode& ec) {
   IndexedDBDispatcher* dispatcher =
       RenderThread::current()->indexed_db_dispatcher();
   dispatcher->RequestIDBCursorDelete(callbacks, idb_cursor_id_, &ec);
 }