Cosmetic filtering causes a layout re-flow during page-load

[petemill]

Cosmetic filtering was enabled (behind a flag) with brave/brave-core#4269

When enabled, it detects which potentially-hidden elements contain 1st party content vs 3rd party content. After the determination, 3rd party content is hidden and 1st party content is left alone. This causes a jump of content when elements are hidden some time after the are first displayed.

Test Plan

0. Enable chrome://flags/#brave-adblock-cosmetic-filtering
1. Visit latimes.com
2. Visit some articles

Actual

Content jumps

Expected

Content is already hidden

[srirambv]

Verification passed on

Brave	1.7.85 Chromium: 80.0.3987.162 (Official Build) dev (64-bit)
Revision	f2c5dd6138153bb0658091205bd1a1717f16081a-refs/branch-heads/3987@{#1034}
OS	Windows 10 OS Version 1803 (Build 17134.523)

Verified using

Brave	1.7.86 Chromium: 80.0.3987.163 (Official Build) (64-bit)
Revision	e7fbe071abe9328cdce4ffedac9822435fbd3656-refs/branch-heads/3987@{#1037}
OS	macOS Version 10.14.6 (Build 18G3020)

• Issue still reproduces as described. Logged follow up issue cosmetic filtering causes a layout re-flow during page-load - follow up to #8197 #9051

Verification passed on

Brave	1.7.86 Chromium: 80.0.3987.163 (Official Build) (64-bit)
Revision	e7fbe071abe9328cdce4ffedac9822435fbd3656-refs/branch-heads/3987@{#1037}
OS	Ubuntu 18.04 LTS

Verified test plan from the description