Bug 1126465 - Implement the ability to disconnect outstanding promises. r=mattwoodrow

dom/media/MediaPromise.cpp

@@ -23,5 +23,18 @@ DispatchMediaPromiseRunnable(nsIEventTarget* aEventTarget, nsIRunnable* aRunnabl
   return aEventTarget->Dispatch(aRunnable, NS_DISPATCH_NORMAL);
 }
 
+void
+AssertOnThread(MediaTaskQueue* aQueue)
+{
+  MOZ_ASSERT(aQueue->IsCurrentThreadIn());
+}
+
+void AssertOnThread(nsIEventTarget* aTarget)
+{
+  nsCOMPtr<nsIThread> targetThread = do_QueryInterface(aTarget);
+  MOZ_ASSERT(targetThread, "Don't know how to deal with threadpools etc here");
+  MOZ_ASSERT(NS_GetCurrentThread() == targetThread);
+}
+
 }
 } // namespace mozilla

dom/media/MediaPromise.h

@@ -37,6 +37,11 @@ namespace detail {
 nsresult DispatchMediaPromiseRunnable(MediaTaskQueue* aQueue, nsIRunnable* aRunnable);
 nsresult DispatchMediaPromiseRunnable(nsIEventTarget* aTarget, nsIRunnable* aRunnable);
 
+#ifdef DEBUG
+void AssertOnThread(MediaTaskQueue* aQueue);
+void AssertOnThread(nsIEventTarget* aTarget);
+#endif
+
 } // namespace detail
 
 /*
@@ -85,9 +90,26 @@ public:
   {
   public:
     NS_INLINE_DECL_THREADSAFE_REFCOUNTING(Consumer)
+
+    void Disconnect()
+    {
+      AssertOnDispatchThread();
+      MOZ_RELEASE_ASSERT(!mComplete);
+      mDisconnected = true;
+    }
+
+#ifdef DEBUG
+    virtual void AssertOnDispatchThread() = 0;
+#else
+    void AssertOnDispatchThread() {}
+#endif
+
   protected:
-    Consumer() {}
+    Consumer() : mComplete(false), mDisconnected(false) {}
     virtual ~Consumer() {}
+
+    bool mComplete;
+    bool mDisconnected;
   };
 
 protected:
@@ -217,9 +239,22 @@ protected:
       MOZ_ASSERT(NS_SUCCEEDED(rv));
     }
 
+#ifdef DEBUG
+  // Can't mark MOZ_OVERRIDE due to bug in clang builders we use for osx b2g desktop. :-(
+  virtual void AssertOnDispatchThread()
+  {
+    detail::AssertOnThread(mResponseTarget);
+  }
+#endif
+
   protected:
     virtual void DoResolve(ResolveValueType aResolveValue) MOZ_OVERRIDE
     {
+      Consumer::mComplete = true;
+      if (Consumer::mDisconnected) {
+        PROMISE_LOG("ThenValue::DoResolve disconnected - bailing out [this=%p]", this);
+        return;
+      }
       InvokeCallbackMethod(mThisVal.get(), mResolveMethod, aResolveValue);
 
       // Null these out after invoking the callback so that any references are
@@ -232,6 +267,11 @@ protected:
 
     virtual void DoReject(RejectValueType aRejectValue) MOZ_OVERRIDE
     {
+      Consumer::mComplete = true;
+      if (Consumer::mDisconnected) {
+        PROMISE_LOG("ThenValue::DoReject disconnected - bailing out [this=%p]", this);
+        return;
+      }
       InvokeCallbackMethod(mThisVal.get(), mRejectMethod, aRejectValue);
 
       // Null these out after invoking the callback so that any references are
@@ -471,6 +511,20 @@ public:
     mConsumer = nullptr;
   }
 
+  // Disconnects and forgets an outstanding promise. The resolve/reject methods
+  // will never be called.
+  void Disconnect() {
+    MOZ_ASSERT(Exists());
+    mConsumer->Disconnect();
+    mConsumer = nullptr;
+  }
+
+  void DisconnectIfExists() {
+    if (Exists()) {
+      Disconnect();
+    }
+  }
+
   bool Exists() { return !!mConsumer; }
 
 private: