Unset CompositorWorkerGlobalScope during WorkerGlobalScope::dipose.

third_party/WebKit/Source/web/CompositorProxyClientImpl.cpp

 // Copyright 2015 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"
 #include "modules/compositorworker/CompositorWorkerGlobalScope.h"
 #include "platform/TraceEvent.h"
 #include "platform/graphics/CompositorMutableStateProvider.h"
@@ skipping 35 matching lines @@
 {
     CompositorProxyClient::trace(visitor);
     visitor->trace(m_mutator);
     visitor->trace(m_globalScope);
     visitor->trace(m_proxies);
 }
 
 void CompositorProxyClientImpl::setGlobalScope(WorkerGlobalScope* scope)
 {
     TRACE_EVENT0("compositor-worker", "CompositorProxyClientImpl::setGlobalScope");
-    DCHECK(!m_globalScope);
-    DCHECK(scope);
+    DCHECK(!m_globalScope || !scope);
     m_globalScope = static_cast<CompositorWorkerGlobalScope*>(scope);
-    m_mutator->registerProxyClient(this);
+    if (m_globalScope)
+        m_mutator->registerProxyClient(this);
 }
 
 void CompositorProxyClientImpl::requestAnimationFrame()
 {
     TRACE_EVENT0("compositor-worker", "CompositorProxyClientImpl::requestAnimationFrame");
     m_requestedAnimationFrameCallbacks = true;
     m_mutator->setNeedsMutate();
 }
 
 bool CompositorProxyClientImpl::mutate(double monotonicTimeNow, CompositorMutableStateProvider* stateProvider)
@@ skipping 26 matching lines @@
 {
     m_proxies.add(proxy);
 }
 
 void CompositorProxyClientImpl::unregisterCompositorProxy(CompositorProxy* proxy)
 {
     m_proxies.remove(proxy);
 }
 
 } // namespace blink