Refactor StringPiece hash.

net/base/linked_hash_map.h

Index: net/base/linked_hash_map.h
diff --git a/net/base/linked_hash_map.h b/net/base/linked_hash_map.h
index b86654bdeeb644d4f46b353499c1b2bf894a0cc1..e3d12d63413727e160487fad23827c7684b6aa99 100644
--- a/net/base/linked_hash_map.h
+++ b/net/base/linked_hash_map.h
@@ -18,9 +18,9 @@
 #include <stddef.h>
 
 #include <list>
+#include <unordered_map>
 #include <utility>
 
-#include "base/containers/hash_tables.h"
 #include "base/logging.h"
 #include "base/macros.h"
 
@@ -30,11 +30,11 @@
 //
 // We also keep a map<Key, list::iterator> for find.  Since std::list is a
 // doubly-linked list, the iterators should remain stable.
-template<class Key, class Value>
+template <class Key, class Value, class Hash = std::hash<Key>>
 class linked_hash_map {
  private:
   typedef std::list<std::pair<Key, Value> > ListType;
-  typedef base::hash_map<Key, typename ListType::iterator> MapType;
+  typedef std::unordered_map<Key, typename ListType::iterator, Hash> MapType;
 
  public:
   typedef typename ListType::iterator iterator;