Revert of Revert of Oilpan: Prepare to make ExecutionContext GarbageCollectedMixin.

Source/platform/heap/Handle.h

Index: Source/platform/heap/Handle.h
diff --git a/Source/platform/heap/Handle.h b/Source/platform/heap/Handle.h
index 203780194d341006cc438cfc192b83c1c6030215..d3872b02be0e526a2361b54a410d1922ab06c8d4 100644
--- a/Source/platform/heap/Handle.h
+++ b/Source/platform/heap/Handle.h
@@ -34,6 +34,7 @@
 #include "platform/heap/Heap.h"
 #include "platform/heap/ThreadState.h"
 #include "platform/heap/Visitor.h"
+#include "wtf/Functional.h"
 #include "wtf/HashFunctions.h"
 #include "wtf/Locker.h"
 #include "wtf/RawPtr.h"
@@ -1152,6 +1153,36 @@
     static const bool value = true;
 };
 
+// For wtf/Functional.h
+template<typename T, bool isGarbageCollected> struct PointerParamStorageTraits;
+
+template<typename T> struct PointerParamStorageTraits<T*, false> {
+    typedef T* StorageType;
+
+    static StorageType wrap(T* value) { return value; }
+    static T* unwrap(const StorageType& value) { return value; }
+};
+
+template<typename T> struct PointerParamStorageTraits<T*, true> {
+    typedef WebCore::CrossThreadPersistent<T> StorageType;
+
+    static StorageType wrap(T* value) { return value; }
+    static T* unwrap(const StorageType& value) { return value.get(); }
+};
+
+// FIXME: This doesn't support collections and const types. See
+// COMPILE_ASSERT_IS_GARBAGE_COLLECTED.
+template<typename T> struct ParamStorageTraits<T*> : public PointerParamStorageTraits<T*, WTF::IsSubclassOfTemplate<T, WebCore::GarbageCollected>::value || WebCore::IsGarbageCollectedMixin<T>::value> {
+};
+
+// We assume RawPtr<T> is used only for garbage-collected types.
+template<typename T> struct ParamStorageTraits<RawPtr<T> > {
+    typedef WebCore::CrossThreadPersistent<T> StorageType;
+
+    static StorageType wrap(RawPtr<T> value) { return value.get(); }
+    static T* unwrap(const StorageType& value) { return value.get(); }
+};
+
 } // namespace WTF
 
 #endif