Bug 70128 – onload handlers fire in incorrect order when iframes are present

• Status: UNCONFIRMED
• Component: Page Loading

Created attachment 111041 [details]
minimal case reproducing the bug

Given three onload handlers: for the top-level document, for the iframe element in that was added to the DOM in inline Javascript block, and for the document inside the iframe, the onload handlers sometimes fire in a wrong order. In particular, the top-level document onload handler fires first, followed by the iframe document onload handler, followed by the iframe element onload handler. I don't know what is the standard-prescribed behavior, but both Mozilla/Firefox and recent versions of IE fire off the handlers in a more sane order: iframe document onload handler followed by the iframe element onload handler followed by the top-level document onload handler. Please see the minimal test case attached.

I also noticed in my testing that presence of other DOM elements, such as images, in the top-level document affects the ordering, sometimes causing it to match Firefox and IE behavior, but only sometimes. I was not able to narrow down exactly what causes the behavior to change.

I've initially found this bug in dev-channel Chrome, but I was able to reproduce it in stable Safari builds as well.