Compression extension for WebSocket has been introduced experimentally by https://bugs.webkit.org/show_bug.cgi?id=77522 as x-webkit-deflate-frame. It's now deprecated and permessage-deflate [1] extension is officially being standardized instead. Blink is switching to it. WebKit should also disable it and switch to the new one if it's fine at some point. Compatibility issue of this change is not severe. WebSocket server should still be able to accept WebSocket clients without x-webkit-deflate-frame. - [1] http://tools.ietf.org/html/draft-ietf-hybi-permessage-compression-09
Just informing that I attached a port of Blink's permessage-deflate implementation to https://bugs.webkit.org/show_bug.cgi?id=98840. It depends on the pywebsocket update in https://bugs.webkit.org/show_bug.cgi?id=115863