ArrayBufferView added to WebSocket.send() as valid parameter type

According to W3C (see http://www.w3.org/TR/websockets/#dom-websocket-send), the WebSocket.send() method also accepts ArrayBufferView in addition to string and ArrayBuffer. It works in all current browsers (Chrome, Firefox, Safari, and IE). I added ArrayBufferView to the list of valid parameter types of WebSocket.send() in externs/html5.js