Pages using VWO.com for A/B testing delay before rendering

Similar to #4402, but related to A/B testing code from VWO

Description

Sites using VWO.com for a/b testing, when loaded with shields up, will show up as a blank page while VWO waits for its experiment code to load. Only after a set timeout (which defaults to around 2 seconds), it will show the page as a fallback.

var _vwo_code=function(e){var t=e,i=2e3,n=2500,r=false,o=false,a=document;return{use_existing_jquery:function(){return r},library_tolerance:function(){return n},finish:function(){if(!o){o=true;var e=a.getElementById("_vis_opt_path_hides");if(e)e.parentNode.removeChild(e)}},finished:function(){return o},load:function(e){var t=a.createElement("script");t.src=e;t.type="text/javascript";t.innerText;t.onerror=function(){_vwo_code.finish()};a.getElementsByTagName("head")[0].appendChild(t)},init:function(){settings_timer=setTimeout("_vwo_code.finish()",i);var e=a.createElement("style"),n="body{opacity:0 !important;filter:alpha(opacity=0) !important;background:none !important;}",r=a.getElementsByTagName("head")[0];e.setAttribute("id","_vis_opt_path_hides");e.setAttribute("type","text/css");if(e.styleSheet)e.styleSheet.cssText=n;else e.appendChild(a.createTextNode(n));r.appendChild(e);this.load("//dev.visualwebsiteoptimizer.com/j.php?a="+t+"&u="+encodeURIComponent(a.URL)+"&r="+Math.random());return settings_timer}}}(visualWebsiteOptimizerId);_vwo_settings_timer=_vwo_code.init();

Steps to Reproduce

1. Open Brave, ensure shields are up.
2. Navigate to https://www.drukwerkdeal.nl (or any other site using VWO)
3. Notice the page finishes loading but then takes another 2 seconds to ‘render’.

Actual result:

Page is shown after delay.

Expected result:

Page is shown immediately after loading.

Reproduces how often:

100% of the time

Brave version (brave://version info)

All channels.

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? YES
• Does the issue resolve itself when disabling Brave Rewards? NO
• Is the issue reproducible on the latest version of Chrome? NO

Miscellaneous Information:

Calling _vwo_code.finish() signals to the page that it can be shown and is used in the VWO experiment code as fallback in catch statement.

[pes10k]

One long term solution we’re deploying soon is to support the uBO format for these, so that we can share effort with that project.

Longer term, we’re thinking of a number of ways we can respond dynamically

[pes10k]

This will also happen on a sig subset of these sites: https://publicwww.com/websites/dev.visualwebsiteoptimizer.com/

Triggered by how we do blocking (reporting success and returning nothing). Will come up with a polyfill now for a short term fix