Refactor StringPiece hash.

base/strings/string_piece.h

Index: base/strings/string_piece.h
diff --git a/base/strings/string_piece.h b/base/strings/string_piece.h
index 92634b9362b7dfb405ef7c7210f90688e385d25d..2efc3e95eb3655160c8e5d84d6e52398e66d994c 100644
--- a/base/strings/string_piece.h
+++ b/base/strings/string_piece.h
@@ -28,7 +28,6 @@
 #include <string>
 
 #include "base/base_export.h"
-#include "base/containers/hash_tables.h"
 #include "base/logging.h"
 #include "base/strings/string16.h"
 
@@ -432,8 +431,6 @@ inline bool operator>=(const StringPiece16& x, const StringPiece16& y) {
 BASE_EXPORT std::ostream& operator<<(std::ostream& o,
                                      const StringPiece& piece);
 
-}  // namespace base
-
 // Hashing ---------------------------------------------------------------------
 
 // We provide appropriate hash functions so StringPiece and StringPiece16 can
@@ -442,28 +439,24 @@ BASE_EXPORT std::ostream& operator<<(std::ostream& o,
 // This hash function is copied from base/strings/string16.h. We don't use the
 // ones already defined for string and string16 directly because it would
 // require the string constructors to be called, which we don't want.
-#define HASH_STRING_PIECE(StringPieceType, string_piece)                \
-  std::size_t result = 0;                                               \
-  for (StringPieceType::const_iterator i = string_piece.begin();        \
-       i != string_piece.end(); ++i)                                    \
-    result = (result * 131) + *i;                                       \
-  return result;                                                        \
-
-namespace BASE_HASH_NAMESPACE {
-
-template<>
-struct hash<base::StringPiece> {
-  std::size_t operator()(const base::StringPiece& sp) const {
-    HASH_STRING_PIECE(base::StringPiece, sp);
+#define HASH_STRING_PIECE(StringPieceType, string_piece)         \
+  std::size_t result = 0;                                        \
+  for (StringPieceType::const_iterator i = string_piece.begin(); \
+       i != string_piece.end(); ++i)                             \
+    result = (result * 131) + *i;                                \
+  return result;
+
+struct StringPieceHash {
+  std::size_t operator()(const StringPiece& sp) const {
+    HASH_STRING_PIECE(StringPiece, sp);
   }
 };
-template<>
-struct hash<base::StringPiece16> {
-  std::size_t operator()(const base::StringPiece16& sp16) const {
-    HASH_STRING_PIECE(base::StringPiece16, sp16);
+struct StringPiece16Hash {
+  std::size_t operator()(const StringPiece16& sp16) const {
+    HASH_STRING_PIECE(StringPiece16, sp16);
   }
 };
 
-}  // namespace BASE_HASH_NAMESPACE
+}  // namespace base
 
 #endif  // BASE_STRINGS_STRING_PIECE_H_