Oilpan: Add ThreadState cleanup callbacks for static thread-specific persistent.

third_party/WebKit/Source/platform/heap/Handle.h

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 312 matching lines @@
         Parent::operator=(other);
         return *this;
     }
 
     template<typename U>
     Persistent& operator=(const Member<U>& other)
     {
         Parent::operator=(other);
         return *this;
     }
+
+    // Requests that the thread state clear this handle when the thread shuts
+    // down. This is intended for use with ThreadSpecific<Persistent<T>>.
+    // It's important that the Persistent<T> exist until then, because this
+    // takes a raw pointer to that handle.
+    //
+    // Example:
+    //   Foo& sharedFoo()
+    //   {
+    //        DEFINE_THREAD_SAFE_STATIC_LOCAL(
+    //            ThreadSpecific<Persistent<Foo>>, threadSpecificFoo,
+    //            new ThreadSpecific<Persistent<Foo>>);
+    //        Persistent<Foo>& fooHandle = *threadSpecificFoo;
+    //        if (!fooHandle) {
+    //            fooHandle = new Foo;
+    //            fooHandle.clearOnThreadShutdown();
+    //        }
+    //        return *fooHandle;
+    //   }
+    void clearOnThreadShutdown()
+    {
+        void (*closure)(Persistent<T>*) = [](Persistent<T>* handle)
+        {
+            *handle = nullptr;
+        };
+        ThreadState::current()->registerCleanupHook(WTF::bind(closure, this));
+    }
 };
 
 // WeakPersistent is a way to create a weak pointer from an off-heap object
 // to an on-heap object. The m_raw is automatically cleared when the pointee
 // gets collected.
 //
 // We have to construct and destruct WeakPersistent in the same thread.
 //
 // Note that collections of WeakPersistents are not supported. Use a persistent
 // collection of WeakMembers instead.
@@ skipping 857 matching lines @@
     // into it.
     //
     // TODO(sof): remove this hack once wtf/Functional.h can also work with a type like
     // CrossThreadWeakPersistent<>.
     static WeakPtr<T> unwrap(const StorageType& value) { return WeakPtr<T>(WeakReference<T>::create(value.get())); }
 };
 
 } // namespace WTF
 
 #endif