OwnPtr, OwnArrayPtr: Use copy/move-and-swap for assignment operators

Source/wtf/OwnArrayPtr.h

Index: Source/wtf/OwnArrayPtr.h
diff --git a/Source/wtf/OwnArrayPtr.h b/Source/wtf/OwnArrayPtr.h
index a678159e096f6222d0ef67f281a4adac0eb68cff..ad39900f552f0ac0e7890145065f1fc7f8007758 100644
--- a/Source/wtf/OwnArrayPtr.h
+++ b/Source/wtf/OwnArrayPtr.h
@@ -104,19 +104,17 @@ template<typename T> inline typename OwnArrayPtr<T>::PtrType OwnArrayPtr<T>::lea
 
 template<typename T> inline OwnArrayPtr<T>& OwnArrayPtr<T>::operator=(const PassOwnArrayPtr<T>& o)
 {
-    PtrType ptr = m_ptr;
-    m_ptr = o.leakPtr();
-    ASSERT(!ptr || m_ptr != ptr);
-    deleteOwnedArrayPtr(ptr);
+    ASSERT(!o || o != m_ptr);
+    OwnArrayPtr ptr = o;
+    swap(ptr);
     return *this;
 }
 
 template<typename T> template<typename U> inline OwnArrayPtr<T>& OwnArrayPtr<T>::operator=(const PassOwnArrayPtr<U>& o)
 {
-    PtrType ptr = m_ptr;
-    m_ptr = o.leakPtr();
-    ASSERT(!ptr || m_ptr != ptr);
-    deleteOwnedArrayPtr(ptr);
+    ASSERT(!o || o != m_ptr);
+    OwnArrayPtr ptr = o;
+    swap(ptr);
     return *this;
 }