Add more out of line copy ctors for complex classes.

cc/layers/layer_list_iterator.h

 // Copyright 2016 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 CC_LAYERS_LAYER_LIST_ITERATOR_H_
 #define CC_LAYERS_LAYER_LIST_ITERATOR_H_
 
 #include <stdlib.h>
 #include <vector>
 
 #include "cc/base/cc_export.h"
 
 namespace cc {
 
 class LayerImpl;
 
 // Unlike LayerIterator and friends, these iterators are not intended to permit
 // traversing the RSLL. Rather, they visit a collection of LayerImpls in
 // stacking order. All recursive walks over the LayerImpl tree should be
 // switched to use these classes instead as the concept of a LayerImpl tree is
 // deprecated.
 class CC_EXPORT LayerListIterator {
  public:
   explicit LayerListIterator(LayerImpl* root_layer);
+  LayerListIterator(const LayerListIterator& other);
   virtual ~LayerListIterator();
 
   bool operator==(const LayerListIterator& other) const {
     return current_layer_ == other.current_layer_;
   }
 
   bool operator!=(const LayerListIterator& other) const {
     return !(*this == other);
   }
 
@@ skipping 18 matching lines @@
   // We will only support prefix increment.
   LayerListIterator& operator++() override;
 
  private:
   void DescendToRightmostInSubtree();
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_LIST_ITERATOR_H_