private boolean isMainThread() {
        return mainThreadSupport == null || mainThreadSupport.isMainThread();
    }
Checks if the current thread is running in the main thread.
If there is no main thread support (e.g. non-Android), "true" is always returned. In that case MAIN thread
subscribers are always called in posting thread, and BACKGROUND subscribers are always called from a background
poster.
EventBus/src/org/greenrobot/eventbus/EventBus.java