Re-allow cosmetic filtering to override in-page !important styles after regression

[antonok-edm]

brave/brave-core#12038 originally provided a fix for #20177, allowing cosmetic filters returned by the adblock engine to be injected into pages with a higher precedence than the page's stylesheets.

Unfortunately, the new method used to inject those CSS rules involved creating a new stylesheet for each rule, rather than the previous method which would simply add rules to a single stylesheet. That turned out to have a significant performance impact, especially for some users and websites; it was reverted in brave/brave-core#12950.

There doesn't appear to be a way exposed by Chromium to inject a privileged stylesheet from JS that also works on Android, or from C++ that doesn't involve creating an entire new stylesheet. Fixing this will likely involve patching StyleEngine to support a new stylesheet specifically used for cosmetic filtering.

[antonok-edm]

Note that #13079 fixed it for all cases except for general class/id injections in standard blocking mode. That will be solved in a followup and is tracked in #22474.

[LaurenWags]

Verified with

Brave | 1.38.118 Chromium: 101.0.4951.67 (Official Build) (x86_64)
-- | --
Revision | 8888ee7a24e2c36661ddb9536c35b7d4852a3a98-refs/branch-heads/4951@{#1230}
OS | macOS Version 12.3.1 (Build 21E258)

Test Case #1 - #22030 (comment)

• 1.38.115 Chromium: 101.0.4951.64 - without fix
• 1.38.118 Chromium: 101.0.4951.67 - with fix

Shields enabled:

• Using 1.38.115 Chromium: 101.0.4951.64 - 738s, 549s, 518s, 570s, 632s
• Using 1.38.118 Chromium: 101.0.4951.67 - 580s, 489s, 483s, 484s, 572s

1.38.115 Chromium: 101.0.4951.64 Example	1.38.118 Chromium: 101.0.4951.67 Example

Shields disabled:

• Using 1.38.115 Chromium: 101.0.4951.64 - 445s, 465s, 470s, 450s, 475s
• Using 1.38.118 Chromium: 101.0.4951.67 - 394s, 414s, 380s, 426s, 384s

1.38.115 Chromium: 101.0.4951.64 Example	1.38.118 Chromium: 101.0.4951.67 Example

Test Case #2 -https://www.foodnetwork.com/recipes/food-network-kitchen/classic-shrimp-scampi-8849846

1.38.115 Chromium: 101.0.4951.64 Example	1.38.118 Chromium: 101.0.4951.67 Example

[MadhaviSeelam]

Verification PASSED with

Brave | 1.38.118 Chromium: 101.0.4951.67 (Official Build) (64-bit)
-- | --
Revision | 8888ee7a24e2c36661ddb9536c35b7d4852a3a98-refs/branch-heads/4951@{#1230}
OS | Windows 11 Version 21H2 (Build 22000.675)

Test Case #1 - #22030 (comment)

• 1.38.115 Chromium: 101.0.4951.64 - without fix
• 1.38.118 Chromium: 101.0.4951.67 - with fix

Shields enabled:
*Using 1.38.115 Chromium: 101.0.4951.64: 290ms, 276ms, 298ms. 288ms
*Using 1.38.118 Chromium: 101.0.4951.67: 237ms, 297ms, 287ms. 339ms

1.38.115 Chromium: 101.0.4951.64	1.38.118 Chromium: 101.0.4951.67

Shields disabled:

*Using 1.38.115 Chromium: 101.0.4951.64 - 289ms, 455ms, 252ms, 275ms
*Using 1.38.118 Chromium: 101.0.4951.67 - 217ms, 250ms, 229ms, 287ms

1.38.115 Chromium: 101.0.4951.64 Example	1.38.118 Chromium: 101.0.4951.67

Test Case #2 -https://www.foodnetwork.com/recipes/food-network-kitchen/classic-shrimp-scampi-8849846

1.38.115 Chromium: 101.0.4951.64 Example	1.38.118 Chromium: 101.0.4951.67 Example

[Uni-verse]

Verification Completed using 1.38.118, Chromium 101.0.4951.67 on Samsung GS 21 running Android 12

Test Case 1: https://news.ycombinator.com/item?id=30932095

Shields ON:

1.38.118 : 572s, 702s, 668s, 630s, 504s
1.38.113: 690s, 633s, 596s, 567s, 628s

Shields OFF:

1.38.118: 474s, 622s, 664s, 576s, 404s
1.38.113: 455s, 594s, 487s, 468s, 472s

Test Case 2: https://www.foodnetwork.com/recipes/food-network-kitchen/classic-shrimp-scampi-8849846

1.38.118	1.38.113

[Uni-verse]

Verification Completed using 1.38.118, Chromium 101.0.4951.67 on Samsung Tab S7 running Android 12

Test Case 1: https://news.ycombinator.com/item?id=30932095

Shields ON:

1.38.118 : 731ms, 883ms, 789ms, 766ms, 847ms
1.38.113: 881ms, 755ms, 877ms, 922ms, 840ms

Shields OFF:

1.38.118: 678ms, 713ms, 681ms, 615ms, 627ms
1.38.113: 766ms, 799ms, 706ms, 952ms, 742ms

Test Case 2: https://www.foodnetwork.com/recipes/food-network-kitchen/classic-shrimp-scampi-8849846

1.38.118	1.38.113

[btlechowski]

Verification passed on

Brave	1.38.119 Chromium: 101.0.4951.67 (Official Build) (64-bit)
Revision	8888ee7a24e2c36661ddb9536c35b7d4852a3a98-refs/branch-heads/4951@{#1230}
OS	Ubuntu 18.04 LTS

Test Case 1: https://news.ycombinator.com/item?id=30932095

Shields ON:

1.38.119 : 4.92s, 3.99s, 4.82s, 4.51s, 4.75s
1.38.115: 4.05s, 5.14s, 4.44s, 4.89s, 4.61s

Shields OFF:

1.38.119: 6.05s, 5.41s, 5.89s, 5.38s, 6.01s
1.38.115: 5.42s, 5.24s, 5.59s, 5.55s, 6.10s

Test Case 2: https://www.foodnetwork.com/recipes/food-network-kitchen/classic-shrimp-scampi-8849846

1.38.119	1.38.115