UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36

Steps to reproduce the problem:
1. Go to https://stat-info.cz/chrome-sw-readablestream.html
2. Click the Download button

What is the expected behavior?
1. A ServiceWorker is registered to intercept requests to /download-sw-readablestream
2. Chrome navigates to this URL
3. Fetch event occurs in the ServiceWorker and responds with a ReadableStream
4. Chrome calls ReadableStream's pull method which returns a Promise
5. 16MB chunk is downloaded and enqueued to the ReadableStream
6. ReadableStream is closed and Promise is resolved
7. 16MB file (16777216 bytes) is saved to disk as "file.bin"

What went wrong?
Downloaded file is sometimes missing several (4-20) kilobytes at the end. Here are some tests:

Windows 7 64bit:
71.0.3578.98 - 11 files corrupted, 9 files OK
70.0.3538.77 - 0 files corrupted, 20 files OK
62.0.3202.94 - 0 files corrupted, 20 files OK

Windows 10 64bit:
71.0.3578.98 - 0 files corrupted, 20 files OK
71.0.3578.80 - 0 files corrupted, 20 files OK

Ubuntu 16.04.5 64bit:
71.0.3578.98 - 20 files corrupted, 0 files OK

MacOS 10.14.2:
71.0.3578.98 - 20 files corrupted, 0 files OK

It looks like Chrome's download manager gets wrong file size. See attached screenshot from Windows 7. For corrupted files I could see 15.9MB/15.9MB in download manager and 16.0MB/16.0MB for the good ones.

Did this work before? Yes 70.0.3538.77

Chrome version: 71.0.3578.98  Channel: stable
OS Version: Ubuntu 16.04.5
Flash Version:
 

Deleted: chrome-71-0-3578-98-win7.png 1.8 KB

	chrome-71-0-3578-98-win7.png 1.8 KB View Download