Prepare CompositorWorker for per thread heap

third_party/WebKit/Source/web/CompositorMutatorImpl.h

Index: third_party/WebKit/Source/web/CompositorMutatorImpl.h
diff --git a/third_party/WebKit/Source/web/CompositorMutatorImpl.h b/third_party/WebKit/Source/web/CompositorMutatorImpl.h
index a5281b6caba60853ee152a8e29d8c97071207f01..b36a67112568a2d8b6c23aaa5a1ebe53fb353788 100644
--- a/third_party/WebKit/Source/web/CompositorMutatorImpl.h
+++ b/third_party/WebKit/Source/web/CompositorMutatorImpl.h
@@ -31,12 +31,6 @@ 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;
 
@@ -50,7 +44,7 @@ public:
 private:
     CompositorMutatorImpl();
 
-    using ProxyClients = HeapHashSet<WeakMember<CompositorProxyClientImpl>>;
+    using ProxyClients = Vector<CrossThreadWeakPersistent<CompositorProxyClientImpl>>;
     ProxyClients m_proxyClients;
 
     std::unique_ptr<CustomCompositorAnimationManager> m_animationManager;