Bug 1014418 - Dispatching hardware button event in Gaia

https://bugzilla.mozilla.org/show_bug.cgi?id=1014418
The term `translate` is unclear within the context IMHO. I suggest we do

    var buttonEventType = this.hkm.getButtonEventType();
    // having a falsey buttonEventType value means the event should be ignored by System
    if (!buttonEventType) {
      return;
    }
    this.state.process(buttonEventType);

to make the code more readable.