[animation-worklet] Implement registerAnimator in worklet scope

third_party/WebKit/Source/modules/compositorworker/AnimatorDefinition.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 AnimatorDefinition_h
+#define AnimatorDefinition_h
+
+#include "bindings/core/v8/ScopedPersistent.h"
+#include "platform/heap/Handle.h"
+#include "v8/include/v8.h"
+
+namespace blink {
+
+class ScriptState;
+class Animator;
+
+// This class represents a valid registered Javascript animator. Note that it
+// assumed the argument passed to its constructor have been validated to have
+// proper type.
+// It can be used to instantiate new animators and also to call the Javascript
+// 'animate' callback one a given instance.
+class AnimatorDefinition final
+    : public GarbageCollectedFinalized<AnimatorDefinition> {
+ public:
+  static AnimatorDefinition* create(ScriptState*,
+                                    v8::Local<v8::Function> constructor,
+                                    v8::Local<v8::Function> animate);
+
+  ~AnimatorDefinition();
+  DEFINE_INLINE_TRACE() {}
+
+  Animator* createInstance();
+
+  // Invoke the the Javascript 'animate' callback one the given instance.

[flackr, 2017/03/13 19:04:52]

nit: s/one/on

[majidvp, 2017/03/13 22:07:54]

removed.

+  // TODO(majidvp): should take a list of proxies
+  void animate(v8::Local<v8::Object> animatorInstance);
+
+ private:
+  AnimatorDefinition(ScriptState*,
+                     v8::Local<v8::Function> constructor,
+                     v8::Local<v8::Function> animate);
+
+  RefPtr<ScriptState> m_scriptState;
+
+  // This object keeps the constructor function, and animate function alive.

[flackr, 2017/03/13 19:04:52]

Isn't the animate function kept alive through the constructor's prototype? Or is
this how we ensure that the animate function doesn't change?

[majidvp, 2017/03/13 22:07:53]

Mainly so it does not change. We can choose to look it up per each
invocation though. We allows some interesting dynamic behavior.
But I want to check to see Houdini's thinking here.

[flackr, 2017/03/14 18:30:29]

Let's call out in the comment that we keep the original animate function to
prevent runtime changes to it.

+  // It needs to be destroyed to break a reference cycle between it and the
+  // AnimationWorkletGlobalScope.
+  ScopedPersistent<v8::Function> m_constructor;
+  ScopedPersistent<v8::Function> m_animate;
+};
+
+}  // namespace blink
+
+#endif  // AnimatorDefinition_h