final class NIOWebSocketFrameAggregator
NIOWebSocketFrameAggregator buffers inbound fragmented WebSocketFrame’s and aggregates them into a single WebSocketFrame. It guarantees that a WebSocketFrame with an opcode of .continuation is never forwarded. Frames which are not fragmented are just forwarded without any processing. Fragmented frames are unmasked, concatenated and forwarded as a new WebSocketFrame which is either a .binary or .text frame. extensionData, rsv1, rsv2 and rsv3 are lost if a frame is fragmented because they cannot be concatenated.