Enable per thread heap for database thread

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

Index: third_party/WebKit/Source/platform/heap/Handle.h
diff --git a/third_party/WebKit/Source/platform/heap/Handle.h b/third_party/WebKit/Source/platform/heap/Handle.h
index 69cb7575950ac9f977932624164767e83a43e6da..8a85126999402b48873de25152a86ee8946cf45d 100644
--- a/third_party/WebKit/Source/platform/heap/Handle.h
+++ b/third_party/WebKit/Source/platform/heap/Handle.h
@@ -410,6 +410,12 @@ public:
     template<typename U>
     CrossThreadPersistent(const Member<U>& other) : Parent(other) { }
 
+    CrossThreadPersistent(WTF::HashTableDeletedValueType) : Parent(reinterpret_cast<T*>(-1))
+    {
+    }
+
+    bool isHashTableDeletedValue() const { return *this == reinterpret_cast<T*>(-1); }
+
     T* atomicGet() { return Parent::atomicGet(); }
 
     template<typename U>
@@ -1116,6 +1122,11 @@ struct UntracedMemberHash : MemberHash<T> {
     STATIC_ONLY(UntracedMemberHash);
 };
 
+template <typename T>
+struct CrossThreadPersistentHash : MemberHash<T> {
+    STATIC_ONLY(CrossThreadPersistentHash);
+};
+
 // PtrHash is the default hash for hash tables with members.
 template <typename T>
 struct DefaultHash<blink::Member<T>> {
@@ -1135,6 +1146,12 @@ struct DefaultHash<blink::UntracedMember<T>> {
     using Hash = UntracedMemberHash<T>;
 };
 
+template <typename T>
+struct DefaultHash<blink::CrossThreadPersistent<T>> {
+    STATIC_ONLY(DefaultHash);
+    using Hash = CrossThreadPersistentHash<T>;
+};
+
 template<typename T>
 struct NeedsTracing<blink::Member<T>> {
     STATIC_ONLY(NeedsTracing);