Long time to start up

[tsmaeder]

Bug Description:

Recently, I've noticed that starting the browser version of Theia takes a long time to load on Firefox. I did a reload under the profiler and a lot of time seems to be spent parsing css. The call stack involves setting the innerText of a html element from a method called updateStyle. The only code in Theia that seems to qualify for this is PluginIconService.updateStyle() which is called from the PluginContributionHandler to register icons. This makes sense, since I have the gitlens plugin installed, which registers a bunch of icons.

Steps to Reproduce:

1. Install gitlens
2. yarn browser start
3. Open "localhost:3000" in Firefox.

Additional Information

• Operating System:
• Theia Version:

[tsmaeder]

This one got fixed as a side-effect of #13217