Actually register the BroadcastChannel pre-finalizer.

third_party/WebKit/Source/modules/broadcastchannel/BroadcastChannel.cpp

Index: third_party/WebKit/Source/modules/broadcastchannel/BroadcastChannel.cpp
diff --git a/third_party/WebKit/Source/modules/broadcastchannel/BroadcastChannel.cpp b/third_party/WebKit/Source/modules/broadcastchannel/BroadcastChannel.cpp
index 2e2b11860c87ae3b443aa4bc718df79d7dc23321..81a588bcabf5358fc55d37539e1f3afcac1d81f0 100644
--- a/third_party/WebKit/Source/modules/broadcastchannel/BroadcastChannel.cpp
+++ b/third_party/WebKit/Source/modules/broadcastchannel/BroadcastChannel.cpp
@@ -121,6 +121,8 @@ BroadcastChannel::BroadcastChannel(ExecutionContext* executionContext, const Str
     , m_name(name)
     , m_binding(this)
 {
+    ThreadState::current()->registerPreFinalizer(this);
+
     mojom::blink::BroadcastChannelProviderPtr& provider = getThreadSpecificProvider();
 
     // Local BroadcastChannelClient for messages send from the browser to this channel.