Align base::hash_map with C++11, part 1.

base/containers/hash_tables.h

 // Copyright (c) 2011 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.
 //
 
 //
 // Deal with the differences between Microsoft and GNU implemenations
 // of hash_map. Allows all platforms to use |base::hash_map| and
 // |base::hash_set|.
 //  eg:
@@ skipping 67 matching lines @@
         return static_cast<std::size_t>(value); \
       } \
     }
 
 DEFINE_TRIVIAL_HASH(long long);
 DEFINE_TRIVIAL_HASH(unsigned long long);
 
 #undef DEFINE_TRIVIAL_HASH
 #endif  // !defined(OS_ANDROID)
 
+// To align with C++11's std::hash and MSVC's pre-standard stdext::hash_value,
+// provide a default hash function for raw pointers. Note: const char * is still
+// specialized to hash as a C string. This is consistent with the currently used
+// stdext::hash_value, but not C++11.
+template<typename T>
+struct hash<T*> {
+  std::size_t operator()(T* value) const {
+    return hash<uintptr_t>()(reinterpret_cast<uintptr_t>(value));
+  }
+};
+
 // Implement string hash functions so that strings of various flavors can
 // be used as keys in STL maps and sets.  The hash algorithm comes from the
 // GNU C++ library, in <tr1/functional>.  It is duplicated here because GCC
 // versions prior to 4.3.2 are unable to compile <tr1/functional> when RTTI
 // is disabled, as it is in our build.
 
 #define DEFINE_STRING_HASH(string_type) \
     template<> \
     struct hash<string_type> { \
       std::size_t operator()(const string_type& s) const { \
@@ skipping 157 matching lines @@
 #else
 #error define hash<std::pair<Type1, Type2> > for your compiler
 #endif  // COMPILER
 
 }
 
 #undef DEFINE_PAIR_HASH_FUNCTION_START
 #undef DEFINE_PAIR_HASH_FUNCTION_END
 
 #endif  // BASE_CONTAINERS_HASH_TABLES_H_