Align base::hash_map with C++11, part 2.

cc/surfaces/surface_id.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_SURFACES_SURFACE_ID_H_
 #define CC_SURFACES_SURFACE_ID_H_
 
-#include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 
 namespace cc {
 
 struct SurfaceId {
   SurfaceId() : id(0) {}
   explicit SurfaceId(uint64_t id) : id(id) {}
 
   bool is_null() const { return id == 0; }
 
   uint64_t id;
 };
 
 inline bool operator==(const SurfaceId& a, const SurfaceId& b) {
   return a.id == b.id;
 }
 
 inline bool operator!=(const SurfaceId& a, const SurfaceId& b) {
   return !(a == b);
 }
 
 inline bool operator<(const SurfaceId& a, const SurfaceId& b) {
   return a.id < b.id;
 }
 
 }  // namespace cc
 
 namespace BASE_HASH_NAMESPACE {
-#if defined(COMPILER_MSVC)
-inline size_t hash_value(const cc::SurfaceId& key) {
-  return hash_value(key.id);
-}
-#elif defined(COMPILER_GCC)
 template <>
 struct hash<cc::SurfaceId> {
   size_t operator()(cc::SurfaceId key) const {
     return hash<uint64_t>()(key.id);
   }
 };
-#else
-#error define a hash function for your compiler
-#endif  // COMPILER
 }  // namespace BASE_HASH_NAMESPACE
 
 #endif  // CC_SURFACES_SURFACE_ID_H_