void SurfaceFlinger::onHandleDestroyed(sp<Layer>& layer)
{
    Mutex::Autolock lock(mStateLock);
    // If a layer has a parent, we allow it to out-live it's handle
    // with the idea that the parent holds a reference and will eventually
    // be cleaned up. However no one cleans up the top-level so we do so
    // here.
    if (layer->getParent() == nullptr) {
        mCurrentState.layersSortedByZ.remove(layer);
    }
    markLayerPendingRemovalLocked(layer);

    auto it = mLayersByLocalBinderToken.begin();
    while (it != mLayersByLocalBinderToken.end()) {
        if (it->second == layer) {
            it = mLayersByLocalBinderToken.erase(it);
        } else {
            it++;
        }
    }

    layer.clear();
}

void SurfaceFlinger::markLayerPendingRemovalLocked(const sp<Layer>& layer) {
    mLayersPendingRemoval.add(layer);
    mLayersRemoved = true;
    setTransactionFlags(eTransactionNeeded);
}

• 如果没有父，则从 layersSortedByZ 中移除 layer。标记 layer 移除，设置 mLayersRemoved，并安排一次 transaction。
• 从 mLayersByLocalBinderToken 中移除 layer，最后调用 clear() 清除所有引用。