Make it possible to run experiments on first run on Windows

[mherrmann]

Description

At the moment, Brave on Windows downloads the variations seed on first run - but it only takes effect after a browser restart. This means that we cannot run experiments for first-run behavior.

The goal of this issue is to make it possible to run experiments during first-run use on Windows via Griffin. It requires changes on the devops side as well as in the browser. This issue supersedes the associated devops issue for visibility in release notes and for QA. It is the Windows part of #15229.

Note: For technical reasons, this change will only affect the 1 MB online installer, not the offline installer.

cc @goodov @iefremov @chrismore

Test Plan:

Please make sure that Brave's online and offline installers for Windows still work. For the online installer, please find a way to check whether an expected experiment was run on first run - that is, in the browser session that launches automatically from the online installer.

[kjozwiak]

@brave/qa-team I'll grab this one and run through a few checks/build off the STR/Cases that @mherrmann mentions via #34150 (comment).

[kjozwiak]

@mherrmann unfortunately I don't think the above is working. When launching 1.62.134 Chromium: 120.0.6099.199 for the first time, I don't see any of the studies listed via brave://version. I also double checked and ensured that it wasn't just a UX issue re: maybe the studies are being applied but not listed via brave://version. However, that's not the case. Seems like the Griffin studies are not being applied still the second launch.

STR/Cases:

Against Production

• install 1.62.134 Chromium: 120.0.6099.199 via https://github.com/brave/brave-browser/releases/download/v1.62.134/BraveBrowserStandaloneBetaSetup.exe
• once the browser launches, check brave://version and notice that there's no Griffin studies being listed
• visit https://www.cnn.com and click on any of the articles and click on the Speedreader icon (notice that TTS is not present)
• restart the browser and notice that the Griffin studies are now being applied
  • Speedreader TTS:Speedreader: TTS enabled
• visit the same article and notice that the TTS option is now available (which means that the Griffin study as been applied)

Against Staging

• install 1.62.134 Chromium: 120.0.6099.199 via https://github.com/brave/brave-browser/releases/download/v1.62.134/BraveBrowserStandaloneBetaSetup.exe
• once the browser launches, close the browser and remove \AppData\Local\BraveSoftware\Brave-Browser-Beta
• relaunch the browser with brave.exe --enable-logging=stderr --reset-variation-state --variations-server-url=https://variations.bravesoftware.com/seed
• visit brave://version and notice that the Griffin studies are not being applied
• close/restart the browser once again using brave.exe --enable-logging=stderr --reset-variation-state --variations-server-url=https://variations.bravesoftware.com/seed
• notice the Griffin studies are now visible/being applied via brave://version

Installers Checked:

• BraveBrowserStandaloneBetaSetup.exe (offline installer) - Griffin NOT being applied on first launch
  • Correctly working on second launch once the browser as been restarted (studies listed via brave://version)
• BraveBrowserBetaSetup.exe (online installer) - Griffin NOT being applied on first launch
  • Correctly working on second launch once the browser as been restarted (studies listed via brave://version)

Also quickly checked and ensured that there wasn't any issues re: downloading the seed file on first launch. However, that seems like it's working without issues. Its just not being applied on first launch.

First Launch (Not working)	Second Launch (Working)

[mherrmann]

Thank you for catching this @kjozwiak. I can reproduce the issue and will investigate. One thing I should have made clearer is that the variations seed only gets fetched by the online installer. So I do not expect it to be applied on first run when installing with the offline installer. I will update the issue description.

[kjozwiak]

Created #35232 as a follow up. We'll keep the above as QA/Blocked for the time being. If we manage to get #35232 resolved and uplifted into 1.62.x, we can label the above as QA/No and use #35232 as the QA issue. However, if we don't mange to get the fix into 1.62.x, we'll label the above as QA/No and will verify #35232 once ready.

[MadhaviSeelam]

@kjozwiak This issue is verified via #35232 (comment) so labelling this issue as QA/No.