NoState Prefetch for background WebApp installations

[Mustapha Jaber]

Hi,

I was wondering if we ever considered using NoState Prefetch for background WebApp installation scenarios like Policy app installations. Given that we only need to load PWA manifest and resources associated with it, using NoState Prefetch would help reduce memory used by background WebContents that we create to accomplish this task today. 

This came up as we were looking into performance impact of background installs in Edge. Would love to learn more if this was ever considered as an option.

Thanks,

Mustapha

[Daniel Murphy]

This is an interesting idea! So then we would be able to see the manifest link without actually executing things like javascript.

I would likely expect this to be an 'early exit optimization', as often sites dynamically add the manifest link in the html from javascript.

Do you think it would be possible to:

• Start with a nostate prefetch when installing pwas from policy/sync.
• Try to find a manifest link in that
• If not, then do the full load before trying manifest link check again

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[Mustapha Jaber]

Good point about sites that dynamically add manifest. I'm not familiar yet with NoState Prefetch content and if it's possible to enable JavaScript for it or if we'd have to spin up a new content to load page with JavaScript enabled. Do we have any data on percentage of sites that dynamically add manifest vs static manifest entry? That will probably help determine if it's worth making this optimization.

[Daniel Murphy]

I believe if we log the InstallableStatusCode appropriately, then the relevant code is MANIFEST_URL_CHANGED. I think this is recorded... sometimes in AppBanners.InstallableStatusCode?

I would guess that is accurate? Our UMA shows we hit that at about 0.25% of the time. I'm not sure if it's undercounted or there is bias. - you can look at where we record that UMA here.

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[Daniel Murphy]

Also, there is possible strong bias here as most of the policy installs are going to be on devices that don't upload UMA (I believe most admin users have uma reporting off by default). So - we don't actually know the occurrence of this happening for the sites that matter most. I think the most we can say is that "this happens".

[Mustapha Jaber]

Ok, looks like it would be worth prototyping this maybe behind a feature flag and flight it to see how often we end up having to spin up full content of the page. Created this feature request bug here:  Use NoState Prefetch for background WebApp installations [401039562] - Chromium