cc: Implement RemoveLast for DisplayItemList.

cc/base/sidecar_list_container.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 CC_BASE_SIDECAR_LIST_CONTAINER_H_
 #define CC_BASE_SIDECAR_LIST_CONTAINER_H_
 
 #include "base/logging.h"
 #include "cc/base/list_container.h"
 
@@ skipping 11 matching lines @@
 //
 // TODO(jbroman): It would be nice to be clear about the memory alignment
 // constraints here, but that probably requires closer inspection of
 // ListContainer first.
 template <class BaseElementType>
 class SidecarListContainer {
  public:
   using SidecarDestroyer = void (*)(void* sidecar);
   using Iterator = typename ListContainer<BaseElementType>::Iterator;
   using ConstIterator = typename ListContainer<BaseElementType>::ConstIterator;
+  using ReverseIterator =
+      typename ListContainer<BaseElementType>::ReverseIterator;
+  using ConstReverseIterator =
+      typename ListContainer<BaseElementType>::ConstReverseIterator;
 
   explicit SidecarListContainer(size_t max_size_for_derived_class,
                                 size_t max_size_for_sidecar,
                                 size_t num_of_elements_to_reserve_for,
                                 SidecarDestroyer destroyer)
       : list_(max_size_for_derived_class + max_size_for_sidecar,
               num_of_elements_to_reserve_for),
         destroyer_(destroyer),
         sidecar_offset_(max_size_for_derived_class) {}
   ~SidecarListContainer() { DestroyAllSidecars(); }
@@ skipping 11 matching lines @@
   template <typename DerivedElementType>
   DerivedElementType* AllocateAndCopyFrom(const DerivedElementType* source) {
     return list_.template AllocateAndCopyFrom<DerivedElementType>(source);
   }
 
   void clear() {
     DestroyAllSidecars();
     list_.clear();
   }
 
+  void RemoveLast() {
+    destroyer_(GetSidecar(*list_.rbegin()));
+    list_.RemoveLast();
+  }
+
   // This permits a client to exchange a pointer to an element to a pointer to
   // its corresponding sidecar.
   void* GetSidecar(BaseElementType* element) {
     DCHECK_GT(sidecar_offset_, 0u);
     return reinterpret_cast<char*>(element) + sidecar_offset_;
   }
   const void* GetSidecar(const BaseElementType* element) {
     DCHECK_GT(sidecar_offset_, 0u);
     return reinterpret_cast<const char*>(element) + sidecar_offset_;
   }
 
  private:
   void DestroyAllSidecars() {
     for (auto* element : list_)
       destroyer_(GetSidecar(element));
   }
 
   ListContainer<BaseElementType> list_;
   SidecarDestroyer destroyer_;
   size_t sidecar_offset_;
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_SIDECAR_LIST_CONTAINER_H_