Decouple adblock engines from component loading methods

Initially, adblock engines were only loaded with sources from Brave’s component server. Over time, additional adblock engines were added that load from the browser’s local preferences (custom filters) or from remote 3rd party servers (subscription lists). The code is still structured to support the initial use-case, which is confusing and limits future improvements. Once this is implemented properly, it will unblock future work like being able to combine the engines together for performance reasons, or untangling threading concerns.

This should ultimately be achieved by removing BraveComponent from the AdBlockService inheritance tree, and replacing it with a common SourceProvider interface that is generic enough to be implemented by the necessary components, custom filters loader, or subscription lists.

[antonok-edm]

@LaurenWags in terms of high impact areas, it’d definitely be good to check that ads on popular sites are still blocked consistently (in particular YouTube and perhaps some news sites).

It could be good to double-check the test plan from https://github.com/brave/brave-core/pull/11621. Other than that, I don’t have a good sense of where there might be any issues (or I would have fixed them already 😉). We do have a decent amount of automated test coverage here, but creativity would be appreciated!

[MadhaviSeelam]

Verified ‘Passed’ using

Brave	1.37.89 Chromium: 99.0.4844.51 (Official Build) beta (64-bit)
Revision	d537ec02474b5afe23684e7963d538896c63ac77-refs/branch-heads/4844@{#875}
OS	Windows 11 Version 21H2 (Build 22000.556)

Testcase 1: Verify when Brave flag is enabled, cookie notice is dismissed and when disabled, cookie notice is displayed again

I. Enable #brave-adblock-cookie-list-default in brave://flags

• Install 1.37.x
• Launch Brave
• Visited https://digikey.com
• Cookie notice displayed on the top
• Visit brave://flags and enabled #brave-adblock-cookie-list-default
• Clicked Relaunch to relaunch the browser
• Visited https://digikey.com and verified cookie notice no longer is displayed
• Visited brave://adblock and verified an entry for Easylist-Cookie List - Filter Obtrusive Cookie Notices is available under Additional filters and is checked

II. Disable #brave-adblock-cookie-list-default in brave://flags

• Visited brave://flag and disabled #brave-adblock-cookie-list-default
• Clicked Relaunch to relaunch the browser
• Visited https://digikey.com and verified cookie notice displayed again
• Verified Easylist-Cookie List - Filter Obtrusive Cookie Notices is unchecked

1	2	3	4	5	6	7

Testcase #2 - Verify cookie banner is dismissed with aggressive mode in Shields

I. Enable #brave-adblock-cookie-list-default in brave://flags

• Clean profile
• Visited https://gulfnews.com
• Cookie notice displayed at the bottom
• Visited brave://flags and enabled #brave-adblock-cookie-list-default
• Clicked Relaunch to relaunch the browser
• Visited https://gulfnews.com but the cookie notice still displayed
• Visited brave://adblock and verified an entry for Easylist-Cookie List - Filter Obtrusive Cookie Notices is available and is checked
• Click on the Shields to select to Aggressive mode in `Trackers & ads blocked``
• Verified cookie notice no longer displayed

II. Disable #brave-adblock-cookie-list-default in brave://flags

• Visited brave://flag and disabled #brave-adblock-cookie-list-default
• Clicked Relaunch to relaunch the browser
• Visited https://gulfnews.com and verified cookie notice displayed at the bottom
• Verified Easylist-Cookie List - Filter Obtrusive Cookie Notices in brave://adblock is unchecked

1	2	3	4	5	6	7

Testcase #3 - Manually toggle `Easylist-Cookie List - Filter Obtrusive Cookie Notices’

• Clean profile
• Visited brave://adblock and checked Easylist-Cookie List - Filter Obtrusive Cookie Notices
• Visited brave://flag and enabled #brave-adblock-cookie-list-default
• Clicked Relaunch to relaunch the browser
• Visited https://digikey.com and verified cookie notice is not displayed
• Visited brave://adblock and verified Easylist-Cookie List - Filter Obtrusive Cookie Notices still checked
• Returned to brave://flags disabled #brave-adblock-cookie-list-default flag and restarted the browser.
• Visited brave://adblock and verified an entry for Easylist-Cookie List - Filter Obtrusive Cookie Notices is still checked
• Visited brave://adblock and unchecked Easylist-Cookie List - Filter Obtrusive Cookie Notices
• Visited brave://flags and enabled #brave-adblock-cookie-list-default flag and restarted the browser.
• Visited https://digikey.com and confirmed cookie notice is displayed

1	2	3	4	5	6	7

Note: In addition to above testing, verified Shields functionality works same as expected by comparing 1.37.x with1.36.x .