Enable websocket filtering via SubresourceFilter

chrome/test/data/subresource_filter/websocket_connection.js

Index: chrome/test/data/subresource_filter/websocket_connection.js
diff --git a/chrome/test/data/subresource_filter/websocket_connection.js b/chrome/test/data/subresource_filter/websocket_connection.js
new file mode 100644
index 0000000000000000000000000000000000000000..de43a5a0f3156d7917fdce6b2e1076a9b12bc786
--- /dev/null
+++ b/chrome/test/data/subresource_filter/websocket_connection.js
@@ -0,0 +1,11 @@
+// Note: This JS can run either in a worker or as a script in the main document
+// context.
+function connectWebSocketWithMessageCallback(url, messageCallback) {
+  var ws = new WebSocket(url);
+
+  ws.onopen = () => { ws.send('hello world'); };
+
+  ws.onclose = () => { messageCallback('onclose'); };
+
+  ws.onmessage = () => { messageCallback('onmessage'); };
+}