document.open() and the load event

[annevk]

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[annevk]

@bzbarsky I tried to figure out what browsers do with the load event because of your comments in #10209 and I'm not much wiser. This test passes in Safari and fails everywhere else (it fails in Firefox because Firefox loses the written content; it fails in Chrome and Edge because they dispatch a normal load event on the window).

I did notice that Chrome has some logic for the load event here: https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/Document.cpp?l=3031. And indeed if I don't wait for the iframe's load event, but open() directly, the window's load event won't fire and that seems interoperable across browsers. (I will add that test later as it seems good to have as a baseline.)

[ghost]

Build PASSED

Started: 2018-03-29 12:33:29
Finished: 2018-03-29 12:43:54

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[bzbarsky]

it fails in Firefox because Firefox loses the written content

It fails in Firefox because step_timeout with a 0 delay fires before the load event for the frame and the open/write that load event triggers. Which is totally allowed per spec, because they use different task sources ("DOM manipulation task source" for the load event, "timer task source" for the setTimeout(func, 0) call).

Furthermore, as the test is written right now, the step_timeout bit can even run before parsing of the HTML completes, hence definitely before the load event for the page would fire no matter what's happening with the subframe...

[annevk]

I adjusted the test a bit, but now it fails in no browser.

I think the main difference between browsers is what happens when you invoke the document open steps during the frame's load event.

I'll add something for that.