View source for Firefox OS/Comms/Dialer/USSD-MMI

* Numbers that start with * or #
* Network replies with some carrier-specific information
** ex: how much credit left, or data traffic left, enable/disable voicemail
* Can be transactions
** Can get a reply, interact with the reply, etc
** Very hacky
** Designed for single-SIM
** UI uses window.postMessage, makes testing difficult, uses setTimeouts
* Biggest issues: needs multi-SIM support, needs better testing
* Special function for sending telephony.sendMMI function
** Should use normal telephony.dial function
* Hacks depending on the network
* Whitelist of codes reimplemented on CDMA (normally for GSM) even though it doesn't really have it (we simulate them)
** Covered well by unit testing
* Biggest issues:
** Needs multi-SIM support
** Needs better testing
** Replies can be mixed up
*** 1. You send a message
*** 2. Get an event reply on that connection
*** 3. System message (unrelated) triggered when you get a response
**** Juggling both is not easy
**** What we do: ignore the connection events
**** Only set an event handler for system events
**** In there we try to figure out if it was solicited or not