feat(extensions): BroadcastChannel WPT conformance

Replaces the file-backed provider by an in-memory one because proper
file locking is a hard problem that detracts from the proof of concept.

Teach the WPT runner how to extract tests from .html files because all
the relevant tests in test_util/wpt/webmessaging/broadcastchannel are
inside basics.html and interface.html.

1 files changed, 5 insertions, 0 deletions

diff --git a/cli/tests/workers/broadcast_channel.ts b/cli/tests/workers/broadcast_channel.ts
new file mode 100644
index 000000000..5076e9eb7
--- /dev/null
+++ b/cli/tests/workers/broadcast_channel.ts
@@ -0,0 +1,5 @@
+new BroadcastChannel("intercom").onmessage = function (e) {
+  this.postMessage(e.data);
+};
+
+self.postMessage("go");