datachannel is only used by peerconnection, we should add RTC-prefix before datachannelevent to comply with RTCPeerConnectionIceEvent.

As for DataChannel, we keep it untill we decide to change it.

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13.3 RTCDataChannelEvent

The datachannel event use the RTCDataChannelEvent interface.

Firing a datachannel event named e with a DataChannel channel means that an event with the name e, which does not bubble (except where otherwise stated) and is not cancelable (except where otherwise stated), and which uses the RTCDataChannelEvent interface with the channel attribute set to channel, must be created and dispatched at the given target.

[Constructor(DOMString type, RTCDataChannelEventInit eventInitDict)]
interface RTCDataChannelEvent : Event {
    readonly attribute DataChannel channel;
};
dictionary RTCDataChannelEventInit : EventInit {
    DataChannel channel;
};
13.3.1 Attributes

channel of type DataChannel, readonly
The channel attribute represents the DataChannel object associated with the event.

13.3.2 Dictionary RTCDataChannelEventInit Members

channel of type DataChannel