Issue 4449 - Use 'websocket' type for WebSocket connections

lib/contentPolicy.js

Index: lib/contentPolicy.js
===================================================================
--- a/lib/contentPolicy.js
+++ b/lib/contentPolicy.js
@@ -55,27 +55,28 @@ var Policy = exports.Policy =
     // Treat fetch() the same as XMLHttpRequest,
     // it's essentially the same - merely a more modern API.
     yield ["FETCH", "XMLHTTPREQUEST"];
 
     // Everything else is mapped to itself
     for (let contentType of ["OTHER", "SCRIPT", "IMAGE", "STYLESHEET", "OBJECT",
                              "SUBDOCUMENT", "DOCUMENT", "XMLHTTPREQUEST",
                              "OBJECT_SUBREQUEST", "FONT", "MEDIA", "PING",
-                             "ELEMHIDE", "POPUP", "GENERICHIDE", "GENERICBLOCK"])
+                             "WEBSOCKET", "ELEMHIDE", "POPUP", "GENERICHIDE",
+                             "GENERICBLOCK"])
       yield [contentType, contentType];
   }()),
 
   /**
    * Set of content types that aren't associated with a visual document area
    * @type Set.<string>
    */
   nonVisualTypes: new Set([
     "SCRIPT", "STYLESHEET", "XMLHTTPREQUEST", "OBJECT_SUBREQUEST", "FONT",
-    "PING", "ELEMHIDE", "POPUP", "GENERICHIDE", "GENERICBLOCK"
+    "PING", "WEBSOCKET", "ELEMHIDE", "POPUP", "GENERICHIDE", "GENERICBLOCK"
   ]),
 
   /**
    * Map containing all schemes that should be ignored by content policy.
    * @type Set.<string>
    */
   whitelistSchemes: new Set(),