Support regional and custom cosmetic filters

[antonok-edm]

Resolves brave/brave-browser#4348

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:

I have added some new unit tests to verify that the logic for merging cosmetic filter information from the different sources works as expected.

Manual verification of custom filter application:

1. Open this sample page
2. Ensure there is no blank space under the word "Advertisement" on the right column (default adblock lists)
3. Open brave://adblock in a new tab
4. At the bottom, add the following custom rule to the "Custom Filters" input: myspace.com###articleLeft
5. Return to the sample page and refresh
6. Ensure that there is still no blank space under the "Advertisement" label in the right column
7. Ensure that the text of the article is also hidden

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.

[antonok-edm]

@emerick everything's updated according to your feedback

[emerick]

LGTM

[bsclifton]

@antonok-edm besides automated tests, are there some manual test steps you can provide for QA to try this out?

[pes10k]

@antonok-edm is there an example from the crawl you did over the summer / autumn you could pull out and just copy-paste the URL here? I think that would suffice.

[antonok-edm]

@bsclifton @pes10k I've updated the Test Plan to include the example I used to make sure this works for custom filters. Unfortunately I haven't been able to find any good examples of up-to-date cosmetic filters in regional lists, but it uses the same machinery.

[pes10k]

Terrific! @bsclifton for my two cents, I think @antonok-edm's test plan is sufficient to make sure the relevant functionality is tickled

[bsclifton]

Updated test plan looks perfect! 😄

[kjozwiak]

Verification PASSED on macOS 10.15.3 x64 using the following build:

Brave	1.7.35 Chromium: 80.0.3987.122 (Official Build) nightly (64-bit)
Revision	cf72c4c4f7db75bc3da689cd76513962d31c7b52-refs/branch-heads/3987@{#943}
OS	macOS Version 10.15.3 (Build 19D76)

• Went through the STR outlined via Support regional and custom cosmetic filters #4700 (comment) without any issues

Without the custom filter

Using the custom filter