Move CrossThreadCopier from platform/ to wtf/

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 420d487cb2c0af301e3f82d17f3616d228fb6d22..b9f4e91b62697affa37e3af7dfe35b3f115c8d94 100644
--- a/third_party/WebKit/Source/platform/heap/Persistent.h
+++ b/third_party/WebKit/Source/platform/heap/Persistent.h
@@ -11,6 +11,7 @@
 #include "platform/heap/Visitor.h"
 #include "wtf/Allocator.h"
 #include "wtf/Atomics.h"
+#include "wtf/CrossThreadCopier.h"
 
 namespace blink {
 
@@ -434,6 +435,19 @@ public:
     }
 };
 
+} // namespace blink
+
+namespace WTF {
+
+template<typename T>
+struct CrossThreadCopier<blink::CrossThreadPersistent<T>> : public CrossThreadCopierPassThrough<blink::CrossThreadPersistent<T>> {
+    STATIC_ONLY(CrossThreadCopier);
+};
+
+} // namespace WTF
+
+namespace blink {
+
 // Combines the behavior of CrossThreadPersistent and WeakPersistent.
 template<typename T>
 class CrossThreadWeakPersistent : public PersistentBase<T, WeakPersistentConfiguration, CrossThreadPersistentConfiguration> {
@@ -483,6 +497,19 @@ public:
     }
 };
 
+} // namespace blink
+
+namespace WTF {
+
+template<typename T>
+struct CrossThreadCopier<blink::CrossThreadWeakPersistent<T>> : public CrossThreadCopierPassThrough<blink::CrossThreadWeakPersistent<T>> {
+    STATIC_ONLY(CrossThreadCopier);
+};
+
+} // namespace WTF
+
+namespace blink {
+
 template<typename Collection>
 class PersistentHeapCollectionBase : public Collection {
     // We overload the various new and delete operators with using the WTF PartitionAllocator to ensure persistent