Implement HTMLDataElement#value
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Implement HTMLDataElement#value
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Implements HTMLDialogElement#close
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Implements HTMLDialogElement#close according to [link](https://html.spec.whatwg.org/multipage/#the-dialog-element:dom-dialog-close)
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When loading HTTP requests, initialise the request ID only if devtools
are used, to lessen the pressure put on the RNG initialisation.
This tentatively fixes#11100 on OS X.
Implement Document.referrer
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Adding:
* global event handlers,
* window event handlers,
* document and element handlers,
* and support for BeforeUnloadEvent.
Signed-off-by: Piotr Stankiewicz <bionicrift@gmail.com>
