Able to reproduce the issue on Win 10,Ubuntu 14.04 and Mac 10.12.2 using 55.0.2883.87/95 and canary 57.0.2966.0.
This is a non-regression issue since 35.0.1849.0.

Note: FireFox 50.0.2 is working fine.

Reassigning to "Blink>DOM>Events" which covers 'load' as specified by https://dom.spec.whatwg.org/#events.

Remove Blink>DOM>Events

I'm putting this back in the triage queue for loader, since the load event isn't really a CSS thing. Sorry, not sure what happened with the components here.

The load event is fired when a resource and its dependent resources have finished loading.

https://www.w3.org/TR/DOM-Level-3-Events/#event-type-load

So, this is intended behavior. Changing an element's text content should not fire a load event. I'm not sure why Firefox does that.

#11 -
That specification is actually pretty old and outdated.

The HTML specification does say something about this and looks (to me) like Firefox is actually right -
https://html.spec.whatwg.org/multipage/semantics.html#the-style-element
Under the "Update a style block" section - https://html.spec.whatwg.org/multipage/semantics.html#update-a-style-block - there are some instructions -
> Once the attempts to obtain the style sheet's critical subresources, if any, are complete, or, if the style sheet has no critical subresources, once the style sheet has been parsed and processed, the user agent must, if the loads were successful or there were none, queue a task to fire an event named load at the style element

Since changing the textContent of <style> means reparsing a stylesheet, it should fire a load event, as far as I understand. What do you think?

Ah you are right, changing the text content of <style> should fire a load event at the <style> element. I misread this bug as about the load event at Document. Thanks for pointing it out.

Since this is about text content change, loader is not involved. Routing to Blink>HTML for further triage.

So this is how changing the stylesheet content would kick the CSS parser
and result in dispatching a load event - moving back the owner to style
team.

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The load event is only fired once on a style element:

https://cs.chromium.org/chromium/src/third_party/blink/renderer/core/html/html_style_element.cc?sq=package:chromium&dr=CSs&l=129-130