Don't assert when ServiceWorker::from is passed an empty promise

Source/bindings/v8/V8GarbageCollected.h

Index: Source/bindings/v8/V8GarbageCollected.h
diff --git a/Source/bindings/v8/V8GarbageCollected.h b/Source/bindings/v8/V8GarbageCollected.h
index 0645b6ba7193221c847e1a33ec3bdd2a672fd986..697974839d90431c8aea30cc7f4ab5e49e90cb89 100644
--- a/Source/bindings/v8/V8GarbageCollected.h
+++ b/Source/bindings/v8/V8GarbageCollected.h
@@ -51,12 +51,14 @@ protected:
     V8GarbageCollected(v8::Isolate* isolate)
         : m_isolate(isolate)
         , m_handle(isolate, v8::External::New(isolate, static_cast<T*>(this)))
+        , m_releasedToV8GarbageCollector(false)
     {
     }
 
     v8::Handle<v8::External> releaseToV8GarbageCollector()
     {
         ASSERT(!m_handle.isWeak()); // Call this exactly once.
+        m_releasedToV8GarbageCollector = true;
         v8::Handle<v8::External> result = m_handle.newLocal(m_isolate);
         m_handle.setWeak(static_cast<T*>(this), &weakCallback);
         return result;
@@ -64,7 +66,7 @@ protected:
 
     ~V8GarbageCollected()
     {
-        ASSERT(m_handle.isEmpty());
+        ASSERT(!m_releasedToV8GarbageCollector || m_handle.isEmpty());

[haraken, 2014/06/17 02:46:24]

Can we use m_handle.IsWeak() instead of introducing
m_releasedToV8GarbageCollector? I think you can use ASSERT(m_handle.IsWeak() ||
m_handle.IsEmpty()).

(I'm fine with this CL, but we should remove V8GarbageCollected completely.
V8GarbageCollected is used only by ScriptFunction, and it's just adding a
complexity of unnecessary abstraction.)

[falken, 2014/06/17 03:43:04]

No, m_handle.IsWeak() is false until releaseToV8GarbageCollector() is called. It
should really be (!m_handle.IsWeak() || m_handle.IsEmpty()) but I don't think
that makes sense (I would think m_handle.IsWeak implies it's not empty).
Yeah, I wonder if other classes were planning to use it too?

I also updated the ServiceWorker.cpp bit after talking with yhirano, who pointed
out it's confusing that ServiceWorker continues as normal with the empty
promise. I added a comment and changed the internal state to ContextStopped in
that case.

If things still look OK I'd like to land the patch.

     }
 
     v8::Isolate* isolate() { return m_isolate; }
@@ -79,6 +81,7 @@ private:
 
     v8::Isolate* m_isolate;
     ScopedPersistent<v8::External> m_handle;
+    bool m_releasedToV8GarbageCollector;
 };
 
 } // namespace WebCore