extension: add option to preserve localStorage

[dskloetg]

I tried Chrome's Audit feature for the first time to find out what it is and it destroyed my localStorage without any warning. If I want to destroy my localStorage before running an audit, I can do that myself. But if I want to run an audit with localStorage in tact, there is no way to do that.

1. Destroying localStorage without even a warning causes data loss and is unacceptable.
2. Even with warning, destroying localStorage makes it impossible to audit with localStorage in tact, while not destroying localStorage keeps all options open.

[patrickhulce]

related crbug #1418 #2599

[MisterTicot]

I confirm this is annoying. As a developper I'm actually using the websites I'm coding on a daily basis. I think that the least one can do to ensure all works fine. I have no choice using another browser to do so. It could be argued that's a feature as it force me to navigate my websites with two different browsers. Also a good reset once in a while allow to check that everything is fine for first-time users :D.

No but seriously, as that tool is here to help us producing better code it seems appropriate to fix that quite annoying bug. I can't tell were a discussion would be needed, Saving the datas aside and load them back when auditing is finish shouldn't be too much challenging isn't it?

(By the way thank you for this tool it's good to have anyway 👍 )

[benschwarz]

Even with warning, destroying localStorage makes it impossible to audit with localStorage in tact, while not destroying localStorage keeps all options open.

If you're using Lighthouse on the command line, there's a flag that will keep your storage intact, --disable-storage-reset.

If you're using Lighthouse via chrome devtools, there's a checkbox before you start the audit (This is in Chrome beta channel, but not yet in stable):

As for the extension, I'm not sure. I haven't used it in quite some time.

[MisterTicot]

@benschwarz Hi, thank you for the answer.
Indeed I'm referring to the extension. The only options I found is which audits to perform. I've also found the trick to allow it under private tabs and use it this way. Which may not be so desirable if the browser is used for actual private browsing. The extension should not erase the localcache by default because the browser may actually be used for browsing.

[connorjclark]

Better captured here, duping: #2599

This issue has some specifics re: the extension, but we've begun thinking about ditching the separate impl for the extension and just having it open the DT panel. So it seems we can close this one without losing any feature request.