public synchronized void copyCallbacks(List<C> callbacks) {
        callbacks.clear();
        int numListeners = mCallbacks.size();
        for (int i = 0; i < numListeners; i++) {
            if (!isRemoved(i)) {
                callbacks.add(mCallbacks.get(i));
            }
        }
    }
Modifies <code>callbacks</code> to contain all callbacks in the CallbackRegistry.

@param callbacks modified to contain all callbacks registered to receive events.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/obs/CallbackRegistry.java