Use C++11 features in core/html

Source/core/html/CollectionIndexCache.h

 /*
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 109 matching lines @@
     nodeAt(collection, UINT_MAX);
     ASSERT(isCachedNodeCountValid());
 
     return cachedNodeCount();
 }
 
 template <typename Collection, typename NodeType>
 inline NodeType* CollectionIndexCache<Collection, NodeType>::nodeAt(const Collection& collection, unsigned index)
 {
     if (isCachedNodeCountValid() && index >= cachedNodeCount())
-        return 0;
+        return nullptr;
 
     if (cachedNode()) {
         if (index > cachedNodeIndex())
             return nodeAfterCachedNode(collection, index);
         if (index < cachedNodeIndex())
             return nodeBeforeCachedNode(collection, index);
         return cachedNode();
     }
 
     // No valid cache yet, let's find the first matching element.
     ASSERT(!isCachedNodeCountValid());
     NodeType* firstNode = collection.traverseToFirst();
     if (!firstNode) {
         // The collection is empty.
         setCachedNodeCount(0);
-        return 0;
+        return nullptr;
     }
     setCachedNode(firstNode, 0);
     return index ? nodeAfterCachedNode(collection, index) : firstNode;
 }
 
 template <typename Collection, typename NodeType>
 inline NodeType* CollectionIndexCache<Collection, NodeType>::nodeBeforeCachedNode(const Collection& collection, unsigned index)
 {
     ASSERT(cachedNode()); // Cache should be valid.
     unsigned currentIndex = cachedNodeIndex();
@@ skipping 32 matching lines @@
         if (index < cachedNodeCount() - 1)
             return nodeBeforeCachedNode(collection, index);
         return lastItem;
     }
 
     // Forward traversal from the cached node to the requested index.
     NodeType* currentNode = collection.traverseForwardToOffset(index, *cachedNode(), currentIndex);
     if (!currentNode) {
         // Did not find the node. On plus side, we now know the length.
         setCachedNodeCount(currentIndex + 1);
-        return 0;
+        return nullptr;
     }
     setCachedNode(currentNode, currentIndex);
     return currentNode;
 }
 
 } // namespace blink
 
 #endif // CollectionIndexCache_h