Brave Extension high memory usage with WDP enabled

[atuchin-m]

Description

A memory leak with enabled WebDiscovery Project in Brave Extension.
Community thread: https://community.brave.com/t/memory-leak-with-no-extensions/405082

Steps to Reproduce (need to be clarified)

1. Enable Web Discovery project in brave://settings;
2. Restart the browser;
3. Open ~10 youtube tabs, scrolls them down;
4. (Optional) watch videos for some time, navigate on youtube.com inside the tabs;
5. Check Brave Extension memory usage.

Actual result:

Brave extension memory footprint > 200MB

Expected result:

Brave extension memory footprint < 100MB

Extra details:

1. No issue without enabled WDP;
2. Reloading the background page helps for some time => memory allocation is triggered by the background page;
3. JS memory is ~10-20Mb and most of the memory is taken by DOM elements. For the extension background page use webtools => memory => heap snapshot to inspect it.

[stephendonner]

Verified PASSED using

Brave	1.43.61 Chromium: 104.0.5112.81 (Official Build) beta (x86_64)
Revision	5b7b76419d50f583022568b6764b630f6ddc9208-refs/branch-heads/5112@{#1309}
OS	macOS Version 11.6.8 (Build 20G730)

First, reproduced the issue with 1.42.88:

10 YouTube tabs	0 open tabs (after 5+ min)

Confirmed fixed using 1.43.61.

Steps:

1. install 1.43.61
2. launch Brave
3. open brave://settings/search and toggle Web Discovery Project to On/Enabled
4. load 10 YouTube tabs with high bitrates
5. close all tabs (the window), but don't shut down Brave
6. waited 5-10 minutes

Confirmed memory allocation/use was down from 225 -> 66.1 MB

10 YouTube tabs	0 open tabs (after 5+ min)

[MadhaviSeelam]

Verification PASSED with

Brave | 1.43.67 Chromium: 104.0.5112.81 (Official Build) beta (64-bit)
-- | --
Revision | 5b7b76419d50f583022568b6764b630f6ddc9208-refs/branch-heads/5112@{#1309}
OS | Windows 11 Version 21H2 (Build 22000.856)

Reproduced with 1.42.88

10 YouTube tabs open	0 open tabs(after 5+ min)

After Fix

Steps:

1. install 1.43.67
2. launch Brave
3. open brave://settings/search and toggle Web Discovery Project to On/Enabled
4. load 10 YouTube tabs
5. close all tabs (the window), but don't shut down Brave
6. waited 8-10 minutes

Confirmed memory footprint was down from 236-->36 MB

Step 3	Step 4	Step 6

[btlechowski]

Verification passed on

Brave	1.43.78 Chromium: 104.0.5112.102 (Official Build) beta (64-bit)
Revision	8e5396254975ef939f2ef7d0bd334e48a052b536-refs/branch-heads/5112@{#1478}
OS	Ubuntu 18.04 LTS

First, reproduced the issue with 1.42.x:

Confirmed fixed using 1.43.x.