See also  issue 826868  (although the conclusion there seems to have been that MojoAsyncResourceHandler has the desired behavior)

Thanks for the pointer!

(So just to clarify this won't block Proj-Servicification-Canary until  issue 826868  is fixed while the other issue is marked to block Canary so this will block it too)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/407e4de01e534567b5c9b7e453cbdf7b79f467af

commit 407e4de01e534567b5c9b7e453cbdf7b79f467af
Author: Makoto Shimazu <shimazu@chromium.org>
Date: Mon Jun 11 10:22:29 2018

NetS13nServiceWorker: don't assume OnStartLoadingResponseBody() is called

In the current implementation, ServiceWorkerNewScriptLoader assume that
OnScriptLoadingResponseBody() is called before OnComplete(). However,
MojoAsyncResourceHandler doesn't call it when response body is empty. This CL is
to adopt that based on discussion at  crbug.com/826868 .

Bug:  848606 ,  826868 
Change-Id: I46646fc2d48c51aa89e02d63c057ef42e74ebb7d
Reviewed-on: https://chromium-review.googlesource.com/1088463
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565953}
[modify] https://crrev.com/407e4de01e534567b5c9b7e453cbdf7b79f467af/content/browser/service_worker/service_worker_new_script_loader.cc
[modify] https://crrev.com/407e4de01e534567b5c9b7e453cbdf7b79f467af/content/browser/service_worker/service_worker_new_script_loader.h
[modify] https://crrev.com/407e4de01e534567b5c9b7e453cbdf7b79f467af/content/browser/service_worker/service_worker_new_script_loader_unittest.cc
[modify] https://crrev.com/407e4de01e534567b5c9b7e453cbdf7b79f467af/third_party/WebKit/LayoutTests/TestExpectations