Specify the arguments of initCompositionEvent()

[foolip]

initCompositionEvent() is supported in Blink, EdgeHTML, Gecko and WebKit. Usage is very low but it's still not a good use of time trying to remove it from all engines.

Instead, specify it like this:

void initCompositionEvent(DOMString type,
                          optional boolean bubbles = false,
                          optional boolean cancelable = false,
                          optional Window? view = null,
                          optional DOMString data = "");

See also whatwg/dom#387

[foolip]

@smaug----, do you have a plan for Gecko's locale member/argument? I didn't include it here.

[smaug----]

Hmm, I don't now remember why we have .locale.
@masayuki-nakano might.

[foolip]

@garykac, might you find time to work on this?

[masayuki-nakano]

I have no idea how to implement "locale" attribute for representing native events because it's difficult to map each OS's locale and locale attribute value. If we cannot standardize the mapping solidly in the spec, same IME's locale may be different between browsers and OSes.

[garykac]

Basically what @masayuki-nakano said.

We wanted to do locale, because we feel it would be useful, but we know that it will be a lot of work to specify it properly and we don't have the time to devote to it right now.

[foolip]

OK, for the purposes of this issue we can pretend that locale doesn't exist, just wanted to make sure omitting it wouldn't be a problem.