Align base::hash_map with C++11.

chrome/browser/sync_file_system/drive_backend/metadata_database_index.h

Index: chrome/browser/sync_file_system/drive_backend/metadata_database_index.h
diff --git a/chrome/browser/sync_file_system/drive_backend/metadata_database_index.h b/chrome/browser/sync_file_system/drive_backend/metadata_database_index.h
index 900876867b8354b7918398029fa227f75660eb55..0937aaf668e9e07e271b56e1ad989aadb598c44a 100644
--- a/chrome/browser/sync_file_system/drive_backend/metadata_database_index.h
+++ b/chrome/browser/sync_file_system/drive_backend/metadata_database_index.h
@@ -29,19 +29,12 @@ class ServiceMetadata;
 
 namespace BASE_HASH_NAMESPACE {
 
-#if defined(COMPILER_GCC)
 template<> struct hash<sync_file_system::drive_backend::ParentIDAndTitle> {
   std::size_t operator()(
       const sync_file_system::drive_backend::ParentIDAndTitle& v) const {
     return base::HashInts64(v.parent_id, hash<std::string>()(v.title));
   }
 };
-#elif defined(COMPILER_MSVC)
-inline size_t hash_value(
-    const sync_file_system::drive_backend::ParentIDAndTitle& v) {
-  return base::HashInts64(v.parent_id, hash_value(v.title));
-}
-#endif  // COMPILER
 
 }  // namespace BASE_HASH_NAMESPACE