code: function releaseMemoryObserver() {
    // Only disable on last use.
    if (!memoryObservationCount) {
      return;
    }
    --memoryObservationCount;
    if (memoryObservationCount) {
      return;
    }
  
    // Unlisten for events.
    Services.obs.removeObserver(
        handleMemoryEvent, 'garbage-collection-statistics', false);
  
    // Reset memory notification to its original state.
    resetTemporaryPreference('javascript.options.mem.notify');
  }
docs: Releases a reference to the memory observer, stopping it if this was the
  last reference.