// Ends the registration. After this is called, no more CallbackHandles will be registered.
// It is safe to send a callback if the Transaction doesn't have any Pending callback handles.
status_t TransactionCallbackInvoker::endRegistration(const ListenerCallbacks& listenerCallbacks) {
    std::lock_guard lock(mMutex);

    auto itr = mRegisteringTransactions.find(listenerCallbacks);
    if (itr == mRegisteringTransactions.end()) {
        ALOGE("cannot end a registration that does not exist");
        return BAD_VALUE;
    }

    mRegisteringTransactions.erase(itr);

    return NO_ERROR;
}

mRegisteringTransactions 中移除 ListenerCallbacks。