Align base::hash_map with C++11.

cc/surfaces/surface_id.h

Index: cc/surfaces/surface_id.h
diff --git a/cc/surfaces/surface_id.h b/cc/surfaces/surface_id.h
index fa17286abc33de3826bec634ebaeaf31ac3a330c..6440ddbf489d97fc582f729c869e1e91bcb98ac2 100644
--- a/cc/surfaces/surface_id.h
+++ b/cc/surfaces/surface_id.h
@@ -34,20 +34,12 @@ inline bool operator<(const SurfaceId& a, const SurfaceId& b) {
 }  // 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_