Bug 1776962 - Close SharedWorker on DETH disconnect. r=dom-worker-reviewers,smaug

SharedWorker can be a better lifecycle participant by closing itself
promptly when its global disconnects its DETHs.  This avoids the need
to wait for CC.

Differential Revision: https://phabricator.services.mozilla.com/D191821

dom/workers/sharedworkers/SharedWorker.cpp

@@ -427,6 +427,11 @@ void SharedWorker::GetEventTargetParent(EventChainPreVisitor& aVisitor) {
   DOMEventTargetHelper::GetEventTargetParent(aVisitor);
 }
 
+void SharedWorker::DisconnectFromOwner() {
+  Close();
+  DOMEventTargetHelper::DisconnectFromOwner();
+}
+
 void SharedWorker::ErrorPropagation(nsresult aError) {
   AssertIsOnMainThread();
   MOZ_ASSERT(mActor);

dom/workers/sharedworkers/SharedWorker.h

@@ -62,6 +62,8 @@ class SharedWorker final : public DOMEventTargetHelper {
 
   void GetEventTargetParent(EventChainPreVisitor& aVisitor) override;
 
+  void DisconnectFromOwner() override;
+
   void ErrorPropagation(nsresult aError);
 
   // Methods called from the window.