code: function handleMemoryEvent(subject, topic, json) {
    if (topic != 'garbage-collection-statistics') {
      return;
    }
  
    // Broadcast the event to all active workers.
    // We avoid parsing it here and let the pages handle it.
    for each (injectedTab in injectedTabs) {
      injectedTab.queueDebuggerRecord(['gc', json]);
    }
  }
docs: Handler for memory observation events.
  @param {*} subject Anything.
  @param {string} topic Event name.
  @param {[type]} json JSON string of GC data.