Uninstall event handlers when replacing WebSocket instance

Ensures we don't get "onclose" events from a previous WebSocket that was in the "closing" state

actioncable/app/assets/javascripts/action_cable/connection.coffee

@@ -21,6 +21,7 @@ class ActionCable.Connection
       throw new Error("Existing connection must be closed before opening")
     else
       console.log("[cable] Opening WebSocket, current state is #{@getState()}", Date.now())
+      @uninstallEventHandlers() if @webSocket?
       @webSocket = new WebSocket(@consumer.url)
       @installEventHandlers()
       true
@@ -60,6 +61,11 @@ class ActionCable.Connection
       @webSocket["on#{eventName}"] = handler
     return
 
+  uninstallEventHandlers: ->
+    for eventName of @events
+      @webSocket["on#{eventName}"] = ->
+    return
+
   events:
     message: (event) ->
       {identifier, message, type} = JSON.parse(event.data)