Bug 1559919 - Finish the WorkerHolder cleanup - part 3 - IPCWorkerRef r=asuth

Differential Revision: https://phabricator.services.mozilla.com/D35222

--HG--
extra : moz-landing-system : lando

dom/workers/WorkerRef.cpp

@@ -216,5 +216,41 @@ WorkerPrivate* ThreadSafeWorkerRef::Private() const {
   return mRef->mWorkerPrivate;
 }
 
+// ----------------------------------------------------------------------------
+// IPCWorkerRef
+
+/* static */
+already_AddRefed<IPCWorkerRef> IPCWorkerRef::Create(
+    WorkerPrivate* aWorkerPrivate, const char* aName,
+    std::function<void()>&& aCallback) {
+  MOZ_ASSERT(aWorkerPrivate);
+  aWorkerPrivate->AssertIsOnWorkerThread();
+
+  RefPtr<IPCWorkerRef> ref = new IPCWorkerRef(aWorkerPrivate);
+
+  // This holder doesn't keep the worker alive.
+  UniquePtr<Holder> holder(
+      new Holder(aName, ref, WorkerHolder::AllowIdleShutdownStart));
+  if (NS_WARN_IF(!holder->HoldWorker(aWorkerPrivate, Canceling))) {
+    return nullptr;
+  }
+
+  ref->mHolder = std::move(holder);
+  ref->mCallback = std::move(aCallback);
+
+  return ref.forget();
+}
+
+IPCWorkerRef::IPCWorkerRef(WorkerPrivate* aWorkerPrivate)
+    : WorkerRef(aWorkerPrivate) {}
+
+IPCWorkerRef::~IPCWorkerRef() = default;
+
+WorkerPrivate* IPCWorkerRef::Private() const {
+  MOZ_ASSERT(mHolder);
+  NS_ASSERT_OWNINGTHREAD(IPCWorkerRef);
+  return mWorkerPrivate;
+}
+
 }  // namespace dom
 }  // namespace mozilla

dom/workers/WorkerRef.h

@@ -79,6 +79,23 @@ namespace dom {
  * ThreadSafeWorkerRef can be destroyed in any thread. Internally it keeps a
  * reference to its StrongWorkerRef creator and this ref will be dropped on the
  * correct thread when the ThreadSafeWorkerRef is deleted.
+ *
+ * IPC WorkerRef
+ * ~~~~~~~~~~~~~
+ *
+ * IPDL protocols require a correct shutdown sequence. Because of this, they
+ * need a special configuration:
+ * 1. they need to be informed when the Worker starts the shutting down
+ * 2. they don't want to prevent the shutdown
+ * 3. but at the same time, they need to block the shutdown until the WorkerRef
+ *    is not longer alive.
+ *
+ * Point 1 is a standard feature of WorkerRef; point 2 is similar to
+ * WeakWorkerRef; point 3 is similar to StrongWorkerRef.
+ *
+ * You can create a special IPC WorkerRef using this static method:
+ * mozilla::dom::IPCWorkerRef::Create(WorkerPrivate* aWorkerPrivate,
+ *                                    const char* * aName);
  */
 
 class WorkerPrivate;
@@ -174,6 +191,37 @@ class ThreadSafeWorkerRef final {
   RefPtr<StrongWorkerRef> mRef;
 };
 
+class IPCWorkerRef final : public WorkerRef {
+ public:
+  static already_AddRefed<IPCWorkerRef> Create(
+      WorkerPrivate* aWorkerPrivate, const char* aName,
+      std::function<void()>&& aCallback = nullptr);
+
+  WorkerPrivate* Private() const;
+
+ private:
+  explicit IPCWorkerRef(WorkerPrivate* aWorkerPrivate);
+  ~IPCWorkerRef();
+};
+
+// Template class to keep an Actor pointer, as a raw pointer, in a ref-counted
+// way when passed to lambdas.
+template <class ActorPtr>
+class IPCWorkerRefHelper final {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(IPCWorkerRefHelper);
+
+  explicit IPCWorkerRefHelper(ActorPtr* aActor) : mActor(aActor) {}
+
+  ActorPtr* Actor() const { return mActor; }
+
+ private:
+  ~IPCWorkerRefHelper() = default;
+
+  // Raw pointer
+  ActorPtr* mActor;
+};
+
 }  // namespace dom
 }  // namespace mozilla