cc: Implement RemoveLast for DisplayItemList.

cc/base/list_container.h

 // Copyright 2014 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_LIST_CONTAINER_H_
 #define CC_BASE_LIST_CONTAINER_H_
 
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 
 namespace cc {
 
 // ListContainer is a container type that handles allocating contiguous memory
 // for new elements and traversing through elements with either iterator or
 // reverse iterator. Since this container hands out raw pointers of its
 // elements, it is very important that this container never reallocate its
@@ skipping 116 matching lines @@
     size_t index() const;
 
    protected:
     // This is used to track how many increment has happened since rbegin(). It
     // is used to avoid double increment at places an index reference is
     // needed. For reverse iterator this means rbegin() corresponds to index 0
     // and rend() corresponds to index |size|.
     size_t index_;
   };
 
-  // Unlike the ListContainer method, this one does not invoke element
-  // destructors.
+  // Unlike the ListContainer methods, these do not invoke element destructors.
+  void RemoveLast();
   void EraseAndInvalidateAllPointers(Iterator position);
 
   ConstReverseIterator crbegin() const;
   ConstReverseIterator crend() const;
   ReverseIterator rbegin();
   ReverseIterator rend();
   ConstIterator cbegin() const;
   ConstIterator cend() const;
   Iterator begin();
   Iterator end();
@@ skipping 46 matching lines @@
     for (Iterator i = begin(); i != end(); ++i) {
       i->~BaseElementType();
     }
   }
 
   class Iterator;
   class ConstIterator;
   class ReverseIterator;
   class ConstReverseIterator;
 
+  // Removes the last element of the list and makes its space available for
+  // allocation.
+  void RemoveLast() {
+    DCHECK(!empty());
+    BaseElementType* item = *rbegin();
+    item->~BaseElementType();
+    ListContainerBase::RemoveLast();
+  }
+
   // When called, all raw pointers that have been handed out are no longer
   // valid. Use with caution.
   // This function does not deallocate memory.
   void EraseAndInvalidateAllPointers(Iterator position) {
     BaseElementType* item = *position;
     item->~BaseElementType();
     ListContainerBase::EraseAndInvalidateAllPointers(position);
   }
 
   ConstReverseIterator crbegin() const {
@@ skipping 216 matching lines @@
         ListContainerBase::ConstReverseIterator base_iterator)
         : ListContainerBase::ConstReverseIterator(base_iterator) {}
     friend ConstReverseIterator ListContainer<BaseElementType>::crbegin() const;
     friend ConstReverseIterator ListContainer<BaseElementType>::crend() const;
   };
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_LIST_CONTAINER_H_