Enable websocket filtering via SubresourceFilter

chrome/test/data/subresource_filter/websocket_connection.js

+// Note: This JS can run either in a worker or as a script in the main document
+// context.
+function connectWebSocket(url, inWorker) {
+  function messageMainContext(data) {
+    if (inWorker)
+      self.postMessage(data);
+    else
+      self.postMessage(data, location);
+  }
+  var ws = new WebSocket(url);
+
+  ws.onopen = function() {
+    ws.send('hello world');
+  };
+
+  ws.onclose = function() {
+    messageMainContext('onclose');
+  };
+
+  ws.onmessage = function() {
+    messageMainContext('onmessage');
+  };
+}
+
+self.addEventListener('message', function(e) {
+  // Will only receive a message with a URL in it if this JS is executing in a

[engedy, 2017/03/06 16:31:01]

To make this a bit cleaner, what do you think of:
 -- refactoring connectWebSocket so it takes a url and a callback,
 -- moving the web worker-related stuff from here into a new JS file that
    uses self.importScripts to include this one?

[Charlie Harrison, 2017/03/06 19:22:11]

SGTM. Done

+  // worker.
+  if (e.data.url) {
+    connectWebSocket(e.data.url, true /* inWorker */);
+  }
+});
+