CompositorWorkerProxyClientImpl to CompositorProxy cross thread reference is using WeakMember

third_party/WebKit/Source/web/CompositorProxyClientImpl.cpp

Index: third_party/WebKit/Source/web/CompositorProxyClientImpl.cpp
diff --git a/third_party/WebKit/Source/web/CompositorProxyClientImpl.cpp b/third_party/WebKit/Source/web/CompositorProxyClientImpl.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6a47bc784f0a49f6ba9e3f60abacd49762bc5fe8
--- /dev/null
+++ b/third_party/WebKit/Source/web/CompositorProxyClientImpl.cpp
@@ -0,0 +1,28 @@
+// 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.
+
+#include "web/CompositorProxyClientImpl.h"
+
+#include "core/dom/CompositorProxy.h"
+
+namespace blink {
+
+DEFINE_TRACE(CompositorProxyClientImpl) {
+  visitor->trace(m_proxies);
+  CompositorProxyClient::trace(visitor);
+}
+
+void CompositorProxyClientImpl::registerCompositorProxy(
+    CompositorProxy* proxy) {
+  DCHECK(!isMainThread());
+  m_proxies.insert(proxy);
+}
+
+void CompositorProxyClientImpl::unregisterCompositorProxy(
+    CompositorProxy* proxy) {
+  DCHECK(!isMainThread());
+  m_proxies.erase(proxy);
+}
+
+}  // namespace blink