CompositorWorkerProxyClientImpl to CompositorProxy cross thread reference is using WeakMember

third_party/WebKit/Source/web/CompositorMutatorImpl.cpp

 // 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.
 
 #include "web/CompositorMutatorImpl.h"
 
 #include "core/animation/CustomCompositorAnimationManager.h"
 #include "core/dom/CompositorProxy.h"
 #include "platform/CrossThreadFunctional.h"
 #include "platform/WaitableEvent.h"
@@ skipping 58 matching lines @@
   for (CompositorAnimator* animator : m_animators) {
     if (animator->mutate(monotonicTimeNow, stateProvider))
       needToReinvoke = true;
   }
 
   return needToReinvoke;
 }
 
 void CompositorMutatorImpl::registerCompositorAnimator(
     CompositorAnimator* animator) {
+  DCHECK(!isMainThread());
   TRACE_EVENT0("compositor-worker",
                "CompositorMutatorImpl::registerCompositorAnimator");
   DCHECK(!m_animators.contains(animator));
   m_animators.insert(animator);
   setNeedsMutate();
 }
 
 void CompositorMutatorImpl::unregisterCompositorAnimator(
     CompositorAnimator* animator) {
   DCHECK(m_animators.contains(animator));
   m_animators.erase(animator);
 }
 
 void CompositorMutatorImpl::setNeedsMutate() {
+  DCHECK(!isMainThread());
   TRACE_EVENT0("compositor-worker", "CompositorMutatorImpl::setNeedsMutate");
   m_client->setNeedsMutate();
 }
 
 }  // namespace blink