(A little more context: we're not fully convinced if we need MIME sniffing for SW responses yet, so putting this off a bit later)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8e66ad255c0fd51ef0c7bdc713efdd9378c1d921

commit 8e66ad255c0fd51ef0c7bdc713efdd9378c1d921
Author: Tsuyoshi Horo <horo@chromium.org>
Date: Tue Oct 03 11:01:30 2017

Add MIME sniffing for SW test and make redirect tests not to rely on MIME sniffing

Bug:  771118 ,  764224 
Change-Id: Ia7a942644736c21412535a9d01bb183794c202cb
Reviewed-on: https://chromium-review.googlesource.com/697484
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506004}
[modify] https://crrev.com/8e66ad255c0fd51ef0c7bdc713efdd9378c1d921/third_party/WebKit/LayoutTests/FlagExpectations/enable-features=NetworkService
[add] https://crrev.com/8e66ad255c0fd51ef0c7bdc713efdd9378c1d921/third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/mime-sniffing.https.html
[add] https://crrev.com/8e66ad255c0fd51ef0c7bdc713efdd9378c1d921/third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/resources/mime-sniffing-worker.js
[modify] https://crrev.com/8e66ad255c0fd51ef0c7bdc713efdd9378c1d921/third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/resources/navigation-redirect-out-scope.py
[modify] https://crrev.com/8e66ad255c0fd51ef0c7bdc713efdd9378c1d921/third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/resources/navigation-redirect-scope1.py
[modify] https://crrev.com/8e66ad255c0fd51ef0c7bdc713efdd9378c1d921/third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/resources/navigation-redirect-scope2.py

Setting to block S13nSW so we don't lose track of this, even if the ultimate decision might be to WontFix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f45d5c38068ce3aa28a032ba241046dfc0e9ff55

commit f45d5c38068ce3aa28a032ba241046dfc0e9ff55
Author: Tsuyoshi Horo <horo@chromium.org>
Date: Wed Oct 11 05:19:00 2017

Make navigation-preload/redirect.https.html not to rely on MIME sniffing

Bug:  771118 ,  764224 
Change-Id: I11aca4ce5675a633cbc722f0c362c0dc4df0b2da
Reviewed-on: https://chromium-review.googlesource.com/711555
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#507900}
[modify] https://crrev.com/f45d5c38068ce3aa28a032ba241046dfc0e9ff55/third_party/WebKit/LayoutTests/FlagExpectations/enable-features=NetworkService
[modify] https://crrev.com/f45d5c38068ce3aa28a032ba241046dfc0e9ff55/third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/navigation-preload/resources/redirect-scope.py

Apologies, applied the wrong component in bulk.

I'll own this. Do we need a spec discussion on this topic? If implementing MIME sniffing isn't so hard, we may want to consider implementing it to preserve the current behavior anyway?

kinuko, horo: do you recall why we weren't sure this is needed as in comment #1?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8dc3f5ecc928cdfd98b04b3216286c04dda078ae

commit 8dc3f5ecc928cdfd98b04b3216286c04dda078ae
Author: Kenichi Ishibashi <bashi@chromium.org>
Date: Tue May 22 01:34:35 2018

S13nSW: Set Content-Type for synthesized responses in content_browsertests

Some of content_browsertests are timing out because we haven't supported
mime-sniffing in S13nSW code path yet ( issue 771118 ). These tests wait
for <title> being updated but it doesn't happen when a synthesized
response doesn't have 'Content-Type: text/html'. Probably a right fix
would be to support mime-sniffing but it's better to make these tests
independent from mime-sniffing as these tests do nothing with
mime-sniffing. This CL changes results of following tests:

- ServiceWorkerBrowserTest.FetchPageWithSaveData -> PASS
- ServiceWorkerBrowserTest.ResponseFromHTTPSServiceWorkerIsMarkedAsSecure -> CRASH
- ServiceWorkerBrowserTest.ResponseFromHTTPServiceWorkerIsNotMarkedAsSecure -> PASS

Following tests are still timing out because of unexpected behavior:

- ServiceWorkerBrowserTest.ImportsBustMemcache
- ServiceWorkerBrowserTest.Reload

Bug:  715640 ,  771118 
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I14819f2b39bfa83edf9eb5fcbf9950d72fa5b292
Reviewed-on: https://chromium-review.googlesource.com/1067220
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560448}
[modify] https://crrev.com/8dc3f5ecc928cdfd98b04b3216286c04dda078ae/content/test/data/service_worker/add_save_data_to_title.js
[modify] https://crrev.com/8dc3f5ecc928cdfd98b04b3216286c04dda078ae/content/test/data/service_worker/fetch_event_blob.js
[modify] https://crrev.com/8dc3f5ecc928cdfd98b04b3216286c04dda078ae/content/test/data/service_worker/fetch_event_reload.js
[modify] https://crrev.com/8dc3f5ecc928cdfd98b04b3216286c04dda078ae/testing/buildbot/filters/mojo.fyi.network_content_browsertests.filter

kinuko, bashi: This looks like the last remaining meaningful test failure with SW + NetworkService. Let's chat today about what to do here.

It seems to me MIME sniffing is impl in URLLoader at:
https://cs.chromium.org/chromium/src/services/network/url_loader.cc?l=701&rcl=6357cc72c771e3f40f610bed88db805b67580a00

And we're not going to hit that path when going through SW loaders.

I'm wondering why other URL loaders don't need MIME sniffing.

Here is a quick hack to sniff blob response in browser process.
https://chromium-review.googlesource.com/c/chromium/src/+/1094754

I don't think this is reasonable though. This adds additional copies (and IPC rounds I guess?).

Discussed offline. This may not be a blocker for S13nServiceWorker. Lowering the priority for now.

Just for my own notes:
* When a service worker does respondWith(new Response(...)) or respondWith(fetch()), MIME sniffing probably does not happen with S13nSW/Network, but it does with the legacy implementation.
* MIME sniffing is implemented in URLLoader, so you might think it would work for respondWith(fetch()). But the Fetch API explicitly disables MIME sniffing.
* We think it might be OK to not do MIME sniffing for SW responses but it's difficult to add meaningful UMA about it. So we'll proceed without the support and adjust if we see problems.
* If ultimately we need to support this, it could potentially be done by changing the URLLoaderClientImpl or in the SW thread at ServiceWorkerContextClient.
* MIME sniffing for NS was implemented in  issue 746144 .
* There is a WPT test mime-sniffing.https.html that maybe shouldn't be a WPT test, if the spec doesn't mandate MIME sniffing. But it could make sense to keep it, if most browsers support it.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6086ea3268b84b5b81bc7f04cf16e39eff9e2685

commit 6086ea3268b84b5b81bc7f04cf16e39eff9e2685
Author: Matt Falkenhagen <falken@chromium.org>
Date: Tue Jun 12 02:08:59 2018

NetS13nServiceWorker: Disable irrelevant test for MimeSniffingResourceHandler.

The test was written to test an internal quirk of
MimeSniffingResourceHandler, which isn't used with Network Service, and
service worker won't support MIME sniffing for now.

Also the quirk, OnStartLoadingResponseBody() called before OnReceiveResponse(),
seems to violate the contract in url_loader.mojom anyway.

Bug:  715640 ,  771118 
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: If9671b3ad0756157064b577693fbea9a520460f6
Reviewed-on: https://chromium-review.googlesource.com/1095061
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566270}
[modify] https://crrev.com/6086ea3268b84b5b81bc7f04cf16e39eff9e2685/content/browser/service_worker/service_worker_browsertest.cc
[modify] https://crrev.com/6086ea3268b84b5b81bc7f04cf16e39eff9e2685/testing/buildbot/filters/mojo.fyi.network_content_browsertests.filter

I'm now trying to apply mime sniffing by injecting URLLoader at ThrottlingURLLoader at NavigationURLLoaderImpl and ResourceDispatcher.
I'm expecting that issue 858975 will be solved together in that approach.

crrev.com/c/1160133 has landed and wpt/service-workers/service-worker/mime-sniffing.https.html is now passing :D

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a68e7651b3960316853757bb288783c6fe2de64d

commit a68e7651b3960316853757bb288783c6fe2de64d
Author: John Abd-El-Malek <jam@chromium.org>
Date: Mon Aug 13 18:26:31 2018

Mark external/wpt/service-workers/service-worker/mime-sniffing.https.html as fixed with network service.

This was fixed in r580143

TBR=shimazu@chromium.org

Bug:  771118 
Cq-Include-Trybots: luci.chromium.try:linux_mojo
Change-Id: I4766a79d1ddb3c017b35da0ced75f30e2a8113d6
Reviewed-on: https://chromium-review.googlesource.com/1172936
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582644}
[modify] https://crrev.com/a68e7651b3960316853757bb288783c6fe2de64d/third_party/WebKit/LayoutTests/FlagExpectations/enable-features=NetworkService