void TransactionCompletedListener::addSurfaceControlToCallbacks(
        const sp<SurfaceControl>& surfaceControl,
        const std::unordered_set<CallbackId, CallbackIdHash>& callbackIds) {
    std::lock_guard<std::mutex> lock(mMutex);

    for (auto callbackId : callbackIds) {
        mCallbacks[callbackId].surfaceControls.emplace(std::piecewise_construct,
                                                       std::forward_as_tuple(
                                                               surfaceControl->getHandle()),
                                                       std::forward_as_tuple(surfaceControl));
    }
}

• 遍历 callbackIds，从 TransactionCompletedListener::mCallbacks 中获取 TransactionCompletedListener::CallbackTranslation，存放 surfaceControl。

该函数主要作用是，已经调用 Transaction::addTransactionCallback() 分配了 CallbackId，这时有新的 SurfaceControl，所以遍历 callbackIds，更新 mCallbacks 中 SurfaceControl。