[animation-worklet] Implement registerAnimator in worklet scope

third_party/WebKit/Source/modules/compositorworker/Animator.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef Animator_h
+#define Animator_h
+
+#include "platform/bindings/ScopedPersistent.h"
+#include "platform/heap/Handle.h"
+#include "v8/include/v8.h"
+
+namespace blink {
+
+class AnimatorDefinition;
+
+class Animator final : public GarbageCollectedFinalized<Animator> {
+ public:
+  static Animator* Create(v8::Isolate*,
+                          AnimatorDefinition*,
+                          v8::Local<v8::Object> instance);
+  ~Animator();
+  DECLARE_TRACE();
+
+ private:
+  Animator(v8::Isolate*, AnimatorDefinition*, v8::Local<v8::Object> instance);
+
+  // This object keeps the definition object, and animator instance alive.
+  // It needs to be destroyed to break a reference cycle between it and the
+  // AnimationWorkletGlobalScope. The reference cycle is broken at
+  // |AnimationWorkletGlobalScope::Dispose()|.
+  Member<AnimatorDefinition> m_definition;
+  ScopedPersistent<v8::Object> m_instance;

[haraken, 2017/05/20 00:35:29]

Can we use the wrapper tracing? You can trace m_instance from
AnimationWorkletGlobalScope. That way we don't need to worry about the reference
cycle.

(We should make the same change to AudioWorkletGlobalScope.)

[majidvp, 2017/05/24 14:24:16]

That makes sense. I didn't know we have wrapper tracing already implemented \o/
I will switch all worklets to wrapper tracing in a follow up patch.

Here is my WIP: https://codereview.chromium.org/2903703003
Feedback is welcome as I am starting to familiarize myself with the patterns.

+};
+
+}  // namespace blink
+
+#endif  // Animator_h