Initial implementation of P3A (Privacy-Preserving Product Analytics)

[bsclifton]

Fixes brave/brave-browser#6285

More details on our blog here:
https://brave.com/privacy-preserving-product-analytics-p3a/

Detailed list of the questions here:
https://github.com/brave/brave-browser/wiki/P3A

Quick description

This pull request will implement checks for those answers and (if enabled) will send the answers anonymously (see blog post for more details).

The answers are always collected, whether the service is on or off. They are stored as a local_state variable (ex: not part of the profile, not synced, etc). However, the answers only leave the users machine if they have the preference enabled.

New user experience

• Welcome screen is shown at first launch
• Users are notified about P3A in the welcome experience
  

Existing user experience

• Existing users will be shown an info bar upon launch
• It remains until acknowledged (even after relaunching)
• Users can click Disable and it will immediately disable the service and close the infobar
• Hitting Got it or clicking the X will acknowledge this and close the infobar
• Clicking Learn more will go to the blog post

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Android
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that all lint errors/warnings are resolved (npm run lint)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone
• Public documentation has been updated as necessary. For instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protection-Mode
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-compatibility-issues-with-tracking-protection
  • https://github.com/brave/brave-browser/wiki/QA-Guide

Test Plan:

There is a bunch of command-line switches suitable to simplify the testing process (see https://github.com/brave/brave-core/blob/master/components/p3a/brave_p3a_switches.h), as well as detailed logs enabled as follows --vmodule=*/p3a/*=3 --enable-logging=stderr

The possible command-line for testing might look as follows:
brave --vmodule=*/p3a/*=3 --enable-logging=stderr --p3a-upload-interval-seconds=5 --p3a-rotation-interval-seconds=160 --p3a-upload-server-url="http://127.0.0.1/" --p3a-ignore-server-errors --p3a-do-not-randomize-upload-interval

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on.
• All relevant documentation has been updated.

[bradleyrichter]

@bsclifton here is the final text in a screen shot

[bradleyrichter]

text:

Brave Shields blocks the creepy stuff that tries to track you across the web — including most ads. Set Shields to “down” if a site doesn’t seem to be working. Brave uses completely private product analytics to estimate the overall usage of certain features. You can turn this off in Settings.

[bsclifton]

Ready for re-review 😄

[bsclifton]

Reviewing the CI for the last run:

• Android built without problems 👍
• iOS built without problems 👍
• Linux
  • builds fine 👍
  • ran into intermittent failure for network audit (not a blocker)
  • seg faulted during unit tests 🙀 https://staging.ci.brave.com/job/brave-browser-build-pr/job/p3a/32/execution/node/558/log/
• macOS
  • builds fine 👍
  • had a problem during network audit (file not found?)
  • crashes during unit tests 🙀 https://staging.ci.brave.com/job/brave-browser-build-pr/job/p3a/32/execution/node/462/log/
• Windows
  • didn't get a chance to fully run it seems?

Going to restart it here...

[bsclifton]

I pulled down the code locally and was able to reproduce the unit tests failing ☹️

@iefremov can you check this out?

[bsclifton]

UPDATE: Linux and macOS passed great 🎉 Seems CI on Windows isn't running?