Prepare CompositorWorker for per thread heap

third_party/WebKit/Source/web/CompositorMutatorImpl.h

 // Copyright 2016 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 CompositorMutatorImpl_h
 #define CompositorMutatorImpl_h
 
 #include "core/animation/CustomCompositorAnimationManager.h"
 #include "platform/graphics/CompositorMutator.h"
 #include "platform/heap/Handle.h"
@@ skipping 13 matching lines @@
 // animation frames are received from ProxyClients and sent to the compositor to
 // generate a new compositor frame.
 //
 // Should be accessed only on the compositor thread.
 class CompositorMutatorImpl final : public CompositorMutator {
     WTF_MAKE_NONCOPYABLE(CompositorMutatorImpl);
 public:
     static std::unique_ptr<CompositorMutatorClient> createClient();
     static CompositorMutatorImpl* create();
 
-    DEFINE_INLINE_TRACE()
-    {
-        CompositorMutator::trace(visitor);
-        visitor->trace(m_proxyClients);
-    }
-
     // CompositorMutator implementation.
     bool mutate(double monotonicTimeNow, CompositorMutableStateProvider*) override;
 
     void registerProxyClient(CompositorProxyClientImpl*);
+    void unregisterProxyClient(CompositorProxyClientImpl*);
 
     void setNeedsMutate();
 
     void setClient(CompositorMutatorClient* client) { m_client = client; }
     CustomCompositorAnimationManager* animationManager() { return m_animationManager.get(); }
 
 private:
     CompositorMutatorImpl();
 
-    using ProxyClients = HeapHashSet<WeakMember<CompositorProxyClientImpl>>;
+    using ProxyClients = HashSet<CrossThreadPersistent<CompositorProxyClientImpl>>;
     ProxyClients m_proxyClients;
 
     std::unique_ptr<CustomCompositorAnimationManager> m_animationManager;
     CompositorMutatorClient* m_client;
 };
 
 } // namespace blink
 
 #endif // CompositorMutatorImpl_h