Allow CrossThreadPersistent in collections

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

Index: third_party/WebKit/Source/platform/heap/Persistent.h
diff --git a/third_party/WebKit/Source/platform/heap/Persistent.h b/third_party/WebKit/Source/platform/heap/Persistent.h
index 8aa3708af2df13521feaaa734413965cde3ac299..64b03d3a5a5976412dda1f316530dca8c83291c0 100644
--- a/third_party/WebKit/Source/platform/heap/Persistent.h
+++ b/third_party/WebKit/Source/platform/heap/Persistent.h
@@ -77,12 +77,20 @@ public:
         checkPointer();
     }
 
+    PersistentBase(WTF::HashTableDeletedValueType) : m_raw(reinterpret_cast<T*>(-1))
+    {
+        initialize();
+        checkPointer();
+    }
+
     ~PersistentBase()
     {
         uninitialize();
         m_raw = nullptr;
     }
 
+    bool isHashTableDeletedValue() const { return m_raw == reinterpret_cast<T*>(-1); }
+
     template<typename VisitorDispatcher>
     void trace(VisitorDispatcher visitor)
     {
@@ -184,7 +192,7 @@ private:
     void initialize()
     {
         ASSERT(!m_persistentNode);
-        if (!m_raw)
+        if (!m_raw || isHashTableDeletedValue())
             return;
 
         TraceCallback traceCallback = TraceMethodDelegate<PersistentBase<T, weaknessConfiguration, crossThreadnessConfiguration>, &PersistentBase<T, weaknessConfiguration, crossThreadnessConfiguration>::trace>::trampoline;
@@ -202,14 +210,15 @@ private:
 
     void uninitialize()
     {
+        if (!m_persistentNode)

[sof, 2016/05/25 13:11:42]

Moving this up here (again) will lead to a race.

+            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());
         // Persistent handle must be created and destructed in the same thread.
@@ -221,7 +230,7 @@ private:
     void checkPointer()
     {
 #if ENABLE(ASSERT) && defined(ADDRESS_SANITIZER)
-        if (!m_raw)
+        if (!m_raw || isHashTableDeletedValue())
             return;
 
         // ThreadHeap::isHeapObjectAlive(m_raw) checks that m_raw is a traceable
@@ -372,6 +381,7 @@ public:
     CrossThreadPersistent(const CrossThreadPersistent<U>& other) : Parent(other) { }
     template<typename U>
     CrossThreadPersistent(const Member<U>& other) : Parent(other) { }
+    CrossThreadPersistent(WTF::HashTableDeletedValueType x) : Parent(x) { }
 
     T* atomicGet() { return Parent::atomicGet(); }
 
@@ -682,6 +692,17 @@ template<typename T, typename U> inline bool operator!=(const Persistent<T>& a,
 
 namespace WTF {
 
+template <typename T>
+struct CrossThreadPersistentHash : MemberHash<T> {
+    STATIC_ONLY(CrossThreadPersistentHash);
+};
+
+template <typename T>
+struct DefaultHash<blink::CrossThreadPersistent<T>> {
+    STATIC_ONLY(DefaultHash);
+    using Hash = CrossThreadPersistentHash<T>;
+};
+
 template<typename T>
 struct ParamStorageTraits<blink::WeakPersistentThisPointer<T>> {
     STATIC_ONLY(ParamStorageTraits);