Enable websocket filtering via SubresourceFilter

chrome/test/data/subresource_filter/page_with_websocket.html

Index: chrome/test/data/subresource_filter/page_with_websocket.html
diff --git a/chrome/test/data/subresource_filter/page_with_websocket.html b/chrome/test/data/subresource_filter/page_with_websocket.html
new file mode 100644
index 0000000000000000000000000000000000000000..4d4e09f6aa962fa6f8e19087eed8d0068bad8338
--- /dev/null
+++ b/chrome/test/data/subresource_filter/page_with_websocket.html
@@ -0,0 +1,28 @@
+<script src="websocket_connection.js"></script>
+<script>
+// Listens for "onmessage" or "onclose" messages from the websocket, and sends
+// them to the test fixture.
+function connectionListener(e) {
+  if (e.data == "onmessage") {
+    window.domAutomationController.send(true);
+  } else if (e.data == "onclose") {
+    window.domAutomationController.send(false);
+  }
+}
+
+// This page has two modes, one where the websocket connection lives in the
+// document context, and one where it lives in a worker. This is encoded by the
+// extra "inWorker" url param.
+var url = new URL(location);
+if (url.searchParams.get('inWorker')) {
+  var worker = new Worker("websocket_connection.js");
+  worker.addEventListener('message', connectionListener);
+
+  // Redefine connectWebSocket to instead post a message to start the worker.
+  connectWebSocket = function(url) {
+    worker.postMessage({url: url});
+  }
+} else {
+  addEventListener("message", connectionListener);
+}
+</script>