How does web browser decompress the content? Decompress while or after downloading?

I'm measuring the performance to use Gzip and Brotli in server side. To use brotli, it saves the time of downloading. But I cannot find a way to measure how long it takes the browser to decompress the content. Though many tests show the decompression speed is similar between Brotli and Gzip, I still want to test it in real environment. My questions is: 1. If the browser decompresses the content while downloading, then the decompression time doesn't matter because decompression is always faster than downloading. 2. Otherwise, is there a way to measure how long it takes the browser to decompress content?

I'm using Chrome Dev Tools. I can see the size of the content is increasing during download. If I enable the large view mode, I can also see the decompressed size is also increasing, so I suspect it decompresses while downwloading