> - when a suresource is unsafe, cancel the other subresources. Seems hard to do, 
> because these resources are not attached to a WebContents or PrerenderContents 
> and there is no easy way to get at them.

This seems like a good idea to me. Perhaps we should talk with SafeBrowsing people to see what their general plans are. In particular, we should have a coherent story for this across all of our speculative fetching actions.

This can of course be done in parallel with the other tasks you mention.

For non-prefetched pages now, a bad subresource will trigger an interstitial but won't block other (good) subresources on the page -- they'll continue to load.

(FYI we're considering a revamp of interstitials in the next two quarters that'd likely change this, maybe with a committed navigation to the interstitial such that subresources would not continue to load.)

And I'd agree, less coupling is good.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/316b5bbb9d35045363bd3954f7c3a68951314cd8

commit 316b5bbb9d35045363bd3954f7c3a68951314cd8
Author: droger <droger@chromium.org>
Date: Tue Jan 10 09:59:39 2017

[NoStatePrefetch] Implement FINAL_STATUS_SAFEBROWSING

This CL plumbs through FINAL_STATUS_SAFEBROWSING for NoStatePrefetch.
The SafeBrowsing throttle attempts to destroy the prefetch if the
main resource is unsafe.

If a subresource is unsafe, it is cancelled, but the network requests
for other subresources on the same page will typically NOT be canceled.
The issue of subresources will be addressed separately in the future.

BUG= 678941 

Review-Url: https://codereview.chromium.org/2615883003
Cr-Commit-Position: refs/heads/master@{#442543}

[modify] https://crrev.com/316b5bbb9d35045363bd3954f7c3a68951314cd8/chrome/browser/loader/safe_browsing_resource_throttle.cc
[modify] https://crrev.com/316b5bbb9d35045363bd3954f7c3a68951314cd8/chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc

The tests have been added.

The only question left is what to do with unsafe subresources. The current behavior is to block them, but not cancel the other subresources.

This is similar to a normal load (as per comment #3), but different from a prerender (which cancels the whole prerender when a unsafe resource is found).

It seems to me that this behavior is acceptable, at least for now, and I'd be tempted to close this bug.

> This is similar to a normal load (as per comment #3), but different from a
> prerender (which cancels the whole prerender when a unsafe resource is found).

But an unknown number of other subresources will still be loaded. What happens to subresource loads that are in-flight when an unsafe subresource is found?

Currently with prefetch, if a subresource is unsafe, it will be blocked, but all other subresources are loaded normally.

In my understanding (as per comment #3), the same thing happens when doing a normal load: everything but the unsafe resource is loaded. In the case of a normal load, a warning page (interstitial) is displayed in this case.

Closing, considering the behavior is good enough.