SAN FRANCISCO : The popular mobile messaging application WhatsApp, acquired by Facebook last year for nearly $22 billion, unveiled a new service Wednesday for sending messages from a Web browser. WhatsApp, which claims some 500 million users, said its Web service will be a ‘mirror’ and would require an Internet-connected phone to work. ‘Our Web client is simply an extension of your phone: the Web browser mirrors conversations and messages from your mobile device - this means all of your messages still live on your phone,’ WhatsApp said in a blog post.