Let's take a step back on that one.
It seems that isReload provides value over the fetch cache attribute (i.e. more resilient and ergonomic)

> It seems that isReload provides value over the fetch cache attribute (i.e. more resilient and ergonomic)

If we are going to keep it, then its behavior for sub-resources needs to be defined.  The spec was previously quite vague about it.

I proposed one way to clarify the behavior here:

https://github.com/whatwg/fetch/issues/524#issuecomment-294507016

ExternalDependency since the spec discussions are not settled.

Note that FetchEvent.isReload is currently not implemented well. See  issue 648761 ,  issue 627481 ,  issue 579866 . If we keep it we need to improve the implementation.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/900dcae2261ada401d6244235def48dedb976619

commit 900dcae2261ada401d6244235def48dedb976619
Author: Matt Falkenhagen <falken@chromium.org>
Date: Wed Jun 28 10:13:22 2017

service worker: Add UseCounter for FetchEvent#isReload

This feature is at-risk and we need to measure usage.

This patch also fixes a bug where use counter for a page wasn't updated for
features used by the service worker during the main resource load.

Bug: 652994, 737355 
Change-Id: Ib62e6c3ea4d1f39345a978c6c8c6c752fc1bd022
Reviewed-on: https://chromium-review.googlesource.com/549539
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#482935}
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/content/child/service_worker/service_worker_dispatcher.cc
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/content/child/service_worker/service_worker_provider_context.cc
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/content/child/service_worker/service_worker_provider_context.h
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/content/child/service_worker/web_service_worker_provider_impl.cc
[add] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/use-isReload-worker.js
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/resources/usecounter-window.html
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/third_party/WebKit/LayoutTests/http/tests/serviceworker/chromium/usecounter.html
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/third_party/WebKit/Source/modules/serviceworkers/FetchEvent.cpp
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/third_party/WebKit/public/platform/WebFeature.h
[modify] https://crrev.com/900dcae2261ada401d6244235def48dedb976619/tools/metrics/histograms/enums.xml

We can start deprecating this since isReloadNavigation is landing soon.