Stop calling Persistent::uninitialize after blink::shutdown is called.

third_party/WebKit/Source/platform/heap/Persistent.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 Persistent_h
 #define Persistent_h
 
 #include "platform/heap/Heap.h"
 #include "platform/heap/Member.h"
 #include "platform/heap/PersistentNode.h"
@@ skipping 206 matching lines @@
         ThreadState* state = ThreadStateFor<ThreadingTrait<T>::Affinity>::state();
         ASSERT(state->checkThread());
         m_persistentNode = state->getPersistentRegion()->allocatePersistentNode(this, traceCallback);
 #if ENABLE(ASSERT)
         m_state = state;
 #endif
     }
 
     void uninitialize()
     {
+        // TODO(haraken): This is a short-term hack to prevent use-after-frees
+        // during a shutdown sequence.
+        // 1) blink::shutdown() frees the underlying storage for persistent nodes.
+        // 2) ~MessageLoop() destructs some Chromium-side objects that hold
+        //    Persistent. It touches the underlying storage and crashes.
+        if (WTF::isShutdown())
+          return;
+
         if (crossThreadnessConfiguration == CrossThreadPersistentConfiguration) {
             if (acquireLoad(reinterpret_cast<void* volatile*>(&m_persistentNode)))
                 ProcessHeap::crossThreadPersistentRegion().freePersistentNode(m_persistentNode);
             return;
         }
 
         if (!m_persistentNode)
             return;
         ThreadState* state = ThreadStateFor<ThreadingTrait<T>::Affinity>::state();
         ASSERT(state->checkThread());
@@ skipping 525 matching lines @@
 
 template <typename T>
 struct IsWeakReceiver<blink::WeakPersistent<T>> : std::true_type {};
 
 template <typename T>
 struct IsWeakReceiver<blink::CrossThreadWeakPersistent<T>> : std::true_type {};
 
 }
 
 #endif // Persistent_h