void LayerTilerChromium::invalidateRect(const IntRect& contentRect)
{
    if (contentRect.isEmpty())
        return;

    growLayerToContain(contentRect);

    IntRect layerRect = contentRectToLayerRect(contentRect);

    int left, top, right, bottom;
    contentRectToTileIndices(contentRect, left, top, right, bottom);
    for (int j = top; j <= bottom; ++j) {
        for (int i = left; i <= right; ++i) {
            Tile* tile = m_tiles[tileIndex(i, j)].get();
            if (!tile)
                continue;
            IntRect bound = tileLayerRect(i, j);
            bound.intersect(layerRect);
            tile->m_dirtyLayerRect.unite(bound);
        }
    }
}

Unknown