Bug 1425975 P1 Add ClientHandle::OnDetach() which returns a MozPromise that resolves on actor destruction. r=asuth

dom/clients/manager/ClientHandle.cpp

@@ -65,6 +65,16 @@ ClientHandle::StartOp(const ClientOpConstructorArgs& aArgs)
   return ref.forget();
 }
 
+void
+ClientHandle::OnShutdownThing()
+{
+  NS_ASSERT_OWNINGTHREAD(ClientHandle);
+  if (!mDetachPromise) {
+    return;
+  }
+  mDetachPromise->Resolve(true, __func__);
+}
+
 ClientHandle::ClientHandle(ClientManager* aManager,
                            nsISerialEventTarget* aSerialEventTarget,
                            const ClientInfo& aClientInfo)
@@ -182,5 +192,21 @@ ClientHandle::PostMessage(StructuredCloneData& aData,
   return ref.forget();
 }
 
+RefPtr<GenericPromise>
+ClientHandle::OnDetach()
+{
+  NS_ASSERT_OWNINGTHREAD(ClientSource);
+
+  if (!mDetachPromise) {
+    mDetachPromise = new GenericPromise::Private(__func__);
+    if (IsShutdown()) {
+      mDetachPromise->Resolve(true, __func__);
+    }
+  }
+
+  RefPtr<GenericPromise> ref(mDetachPromise);
+  return Move(ref);
+}
+
 } // namespace dom
 } // namespace mozilla

dom/clients/manager/ClientHandle.h

@@ -42,6 +42,7 @@ class ClientHandle final : public ClientThing<ClientHandleChild>
 
   RefPtr<ClientManager> mManager;
   nsCOMPtr<nsISerialEventTarget> mSerialEventTarget;
+  RefPtr<GenericPromise::Private> mDetachPromise;
   ClientInfo mClientInfo;
 
   ~ClientHandle();
@@ -52,6 +53,10 @@ class ClientHandle final : public ClientThing<ClientHandleChild>
   already_AddRefed<ClientOpPromise>
   StartOp(const ClientOpConstructorArgs& aArgs);
 
+  // ClientThing interface
+  void
+  OnShutdownThing() override;
+
   // Private methods called by ClientHandleChild
   void
   ExecutionReady(const ClientInfo& aClientInfo);
@@ -90,6 +95,17 @@ public:
   PostMessage(ipc::StructuredCloneData& aData,
               const ServiceWorkerDescriptor& aSource);
 
+  // Return a Promise that resolves when the ClientHandle object is detached
+  // from its remote actors.  This will happen if the ClientSource is destroyed
+  // and triggers the cleanup of the handle actors.  It will also naturally
+  // happen when the ClientHandle is de-referenced and tears down its own
+  // actors.
+  //
+  // Note: This method can only be called on the ClientHandle owning thread,
+  //       but the MozPromise lets you Then() to another thread.
+  RefPtr<GenericPromise>
+  OnDetach();
+
   NS_INLINE_DECL_REFCOUNTING(ClientHandle);
 };
 

dom/clients/manager/ClientThing.h

@@ -90,6 +90,15 @@ protected:
       mActor->MaybeStartTeardown();
       mActor = nullptr;
     }
+
+    OnShutdownThing();
+  }
+
+  // Allow extending classes to take action when shutdown.
+  virtual void
+  OnShutdownThing()
+  {
+    // by default do nothing
   }
 
 public:
@@ -106,6 +115,8 @@ public:
     // instead of calling ShutdownThing() to avoid calling MaybeStartTeardown()
     // on the destroyed actor.
     mShutdown = true;
+
+    OnShutdownThing();
   }
 };