Webpage loading: blank page for several seconds

[fear-the-beaver]

Description

Some webpages like https://tools.usps.com/go/TrackConfirmAction!input.action and https://www.theverge.com/ stay blank for 3-5 seconds before showing the content.

Steps to Reproduce

1. Enable shields in Brave (ads and trackers, HTTPs, block 3rd party cookies and device recognition)
2. Access https://tools.usps.com/go/TrackConfirmAction!input.action or https://www.theverge.com/

Actual result:

1. Blank page is being displayed for 3-5 seconds.
2. Page elements start loading up.

Expected result:

1. Page elements start loading up.

Reproduces how often:

100%

Brave version (brave://version info)

Desktop:

Brave	0.60.48 Chromium: 72.0.3626.121 (Official Build) (64-bit)
Revision	da3787ba355f18db7db52abf75c42afb408d656f-refs/branch-heads/3626@{#883}
OS	Mac OS X

Mobile:

Brave | 1.0.84 Chromium 72.0.3626.121

OS | Android 9

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds?

Not tested

Website problems only:

• Does the issue resolve itself when disabling Brave Shields?

Yes

• Is the issue reproducible on the latest version of Chrome?

Not tested

Additional Information

[ghug]

This seems to be related to these sites' use of Google Optimize's anti-flicker page hiding.

Reproducible on beta and dev, but not in Chrome.

[rebron]

cc: @kjozwiak to check on where this is getting tripped up.

[kjozwiak]

@fear-the-beaver @gabrielhug this was most likely resolved by #4402 and released in 0.66.x on June 25, 2019.

I went through a view cases loading https://www.theverge.com/ and didn't run into any issues. I'm going to close this off. If you're still running into the above issue, please feel free to re-open.