Make FormData a cloneable object

[annevk]

This can be done after whatwg/html#727 lands.

[wisniewskit]

Was this something that should be dealt with now that the referenced landing happened?

[annevk]

Yeah maybe, although I haven't seen much interest. Do you happen to know if in the implementation we effectively clone FormData objects when they are passed to XMLHttpRequest?

[inexorabletash]

FWIW, in Blink's XHR implementation we synchronously serialize the passed FormData; nothing shared with the cloning implementation, no script-visible side effects, etc.

[annevk]

Apparently Firefox already supports this. Is there interest from Chrome in supporting this @inexorabletash? @youennf WebKit? @travisleithead Edge?

[inexorabletash]

SGTM; not high on the priority list but seems doable. Tests would be great.

[jed-meyer]

Apparently Firefox already supports this.

This doesn't hold true (anymore), see dexie/Dexie.js#861

[annevk]

Well,

onmessage = e => console.log(e.data)
postMessage(new FormData(),"*");

does log a FormData object in Firefox Nightly and an exception in Chrome Canary. However, the serialization steps for a given platform object are also passed a forStorage boolean. I suspect Firefox throws if that is true, based on your analysis.

[pavinduLakshan]

Is this now supported?