struct CallbackInfo {
    // All the callbacks that have been requested for a TransactionCompletedListener in the
    // Transaction
    std::unordered_set<CallbackId, CallbackIdHash> callbackIds;
    // All the SurfaceControls that have been modified in this TransactionCompletedListener's
    // process that require a callback if there is one or more callbackIds set.
    std::unordered_set<sp<SurfaceControl>, SCHash> surfaceControls;
};

CallbackInfo 存储在 Transaction 的 mListenerCallbacks 字段，它是一个 map。

std::unordered_map<sp<ITransactionCompletedListener>, CallbackInfo, TCLHash>
        mListenerCallbacks;