Add ListContainer::swap

Source/platform/graphics/ListContainer.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ListContainer_h
 #define ListContainer_h
 
 #include "platform/PlatformExport.h"
 #include "wtf/Forward.h"
 #include "wtf/Noncopyable.h"
@@ skipping 246 matching lines @@
     }
 
     // Construct a new element on top of an existing one.
     template <typename DerivedElementType>
     DerivedElementType* replaceExistingElement(Iterator at)
     {
         at->~BaseElementType();
         return new (*at) DerivedElementType();
     }
 
+    template <typename DerivedElementType>
+    void swap(ListContainer<DerivedElementType>& other)
+    {
+        m_data.swap(other.m_data);
+    }
+
     // Appends a new item without copying. The original item will not be
     // destructed and will be replaced with a new DerivedElementType. The
     // DerivedElementType does not have to match the moved type as a full block
     // of memory will be moved (up to maxSizeForDerivedClass()).
     template <typename DerivedElementType>
     void appendByMoving(DerivedElementType* item)
     {
         size_t maxSize = maxSizeForDerivedClass();
         void* newItem = allocate(maxSize);
         memcpy(newItem, static_cast<void*>(item), maxSize);
@@ skipping 152 matching lines @@
         explicit ConstReverseIterator(ListContainerBase::ConstReverseIterator baseIterator)
             : ListContainerBase::ConstReverseIterator(baseIterator) {}
         friend ConstReverseIterator ListContainer<BaseElementType>::crbegin() const;
         friend ConstReverseIterator ListContainer<BaseElementType>::crend() const;
     };
 };
 
 } // namespace blink
 
 #endif // ListContainer_h