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 209 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();
@@ skipping 563 matching lines @@
   static blink::CrossThreadPersistent<T> Unwrap(
       const blink::CrossThreadWeakPersistent<T>& wrapped) {
     blink::CrossThreadPersistentRegion::LockScope persistentLock(
         blink::ProcessHeap::crossThreadPersistentRegion());
     return blink::CrossThreadPersistent<T>(wrapped.get());
   }
 };
 }
 
 #endif  // Persistent_h