Browser-laptop: UI becomes unresponsive when rapidly creating tabs via `CTRL + T`

[kjozwiak]

- Did you search for similar issues before submitting this one?

Yes

- Describe the issue you encountered:

When rapidly opening a bunch of tabs via "CTRL + T", the Brave UI becomes completely unresponsive after opening 6-15 tabs.

- Platform (Win7, 8, 10? macOS? Linux distro?):

Win 10 x64 - Reproduced
macOS 10.12.6 x64 - Reproduced

- Brave Version (revision SHA):

Brave 0.18.24 rev | 1853c35eeeac8ae271755f5aef71a06ebeef7e83
Muon 4.3.14
libchromiumcontent 60.0.3112.101

- Steps to reproduce:

1. Open Brave 0.18.24 rev | 1853c35eeeac8ae271755f5aef71a06ebeef7e83
2. Rapidly opened a bunch of tabs using CTRL + T

- Actual result:

The entire Brave UI becomes unresponsive

- Expected result:

The Brave UI shouldn't become unresponsive when rapidly opening tabs via CTRL + T

- Will the steps above reproduce in a fresh profile? If not what other info can be added?

Yes

- Is this an issue in the currently released version?

No

- Can this issue be consistently reproduced?

Yes, using the above STR, the issue is 100% reproducible

- Screenshot if needed:

[srirambv]

App is quite slow when opening a lot of tabs on Windows. CPU usage spikes a lot while loading pages on all tabs.

https://github.com/brave/browser-laptop/issues/5419

[luixxiul]

@kjozwiak what is the issue not fixed here?

[cndouglas]

+1 from me (#10866)

[bbondy]

@kjozwiak is this the same as #10866 or no? I can't reproduce this one but I can reproduce #10866.

[bbondy]

Seems different from #10866 (who's fix is to queue events until window is ready). This fix is after window is ready so won't be fixed by a fix like that. Moving this one since @kjozwiak says it's rare to 0.20.x for re-assessment later.

[bsclifton]

From the screenshot by @kjozwiak, this is where it's crashing at (state is null/undefined):
https://github.com/brave/browser-laptop/blob/b47daf7c30c817c1a602342e9e07c736ab1fffa8/js/stores/windowStore.js#L131

This is fired when processing the APP_NEW_WEB_CONTENTS_ADDED action. It seems one of the reducers is returning null or undefined

[kevinp2]

@kjozwiak , what software did you use to record the video / image / animation of the Brave tabs above?

[kjozwiak]

@kjozwiak , what software did you use to record the video / image / animation of the Brave tabs above?

@kevinp2 using a tool called Licecap [1] which captures an area of your desktop and turns it into a .gif file. Really useful tool!

• [1] https://www.cockos.com/licecap/

[kjozwiak]

We're finally going to get rid of this with brave-core 🎉 One of the first issues that I QA'd when I started here which led to this bug + a bunch more!