I will take a look this issue.

The CL is ready to review. (https://chromium-review.googlesource.com/c/chromium/src/+/1179513)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f531aaf8e629237000c645f6046ea2be0857ed66

commit f531aaf8e629237000c645f6046ea2be0857ed66
Author: Dong-hee Na <donghee.na92@gmail.com>
Date: Wed Aug 22 16:49:15 2018

Fetch: Set the response message be an empty string

Update FetchResponseData::Create() to set the
response message to be an empty string unless
the URLs protocol is about or data or blob.

Bug:  832041 
Change-Id: I9e8ec27dd8b4ba051bb97c6ca063f618191c95ce
Reviewed-on: https://chromium-review.googlesource.com/1179513
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Jinho Bang <jinho.bang@samsung.com>
Cr-Commit-Position: refs/heads/master@{#585085}
[modify] https://crrev.com/f531aaf8e629237000c645f6046ea2be0857ed66/AUTHORS
[delete] https://crrev.com/7ae5f4bf5ed54f600b82e13be6f32c24872096c0/third_party/WebKit/LayoutTests/external/wpt/fetch/api/response/response-static-redirect-expected.txt
[modify] https://crrev.com/f531aaf8e629237000c645f6046ea2be0857ed66/third_party/blink/renderer/core/fetch/fetch_manager.cc
[modify] https://crrev.com/f531aaf8e629237000c645f6046ea2be0857ed66/third_party/blink/renderer/core/fetch/fetch_response_data.cc

Now, we can close this issue :)

Fixed by donghee.na92@gmail.com.

Thanks!