[net/http auth] Use strings to identify authentication schemes.

net/http/http_auth_handler_factory.cc

Index: net/http/http_auth_handler_factory.cc
diff --git a/net/http/http_auth_handler_factory.cc b/net/http/http_auth_handler_factory.cc
index 5a89964a80c6d47344e6ab2daa747a92b30b3305..5f24fccf3724c8533cf4d3b930dbed4c65c5b169 100644
--- a/net/http/http_auth_handler_factory.cc
+++ b/net/http/http_auth_handler_factory.cc
@@ -106,13 +106,13 @@ void HttpAuthHandlerRegistryFactory::SetURLSecurityManager(
 void HttpAuthHandlerRegistryFactory::RegisterSchemeFactory(
     const std::string& scheme,
     HttpAuthHandlerFactory* factory) {
-  std::string lower_scheme = base::ToLowerASCII(scheme);
-  FactoryMap::iterator it = factory_map_.find(lower_scheme);
+  DCHECK(HttpAuth::IsValidNormalizedScheme(scheme));
+  FactoryMap::iterator it = factory_map_.find(scheme);
   if (it != factory_map_.end()) {
     delete it->second;
   }
   if (factory)
-    factory_map_[lower_scheme] = factory;
+    factory_map_[scheme] = factory;
   else
     factory_map_.erase(it);
 }
@@ -185,13 +185,12 @@ int HttpAuthHandlerRegistryFactory::CreateAuthHandler(
     int digest_nonce_count,
     const BoundNetLog& net_log,
     scoped_ptr<HttpAuthHandler>* handler) {
-  std::string scheme = challenge->scheme();
+  std::string scheme = challenge->NormalizedScheme();
   if (scheme.empty()) {
     handler->reset();
     return ERR_INVALID_RESPONSE;
   }
-  std::string lower_scheme = base::ToLowerASCII(scheme);
-  FactoryMap::iterator it = factory_map_.find(lower_scheme);
+  FactoryMap::iterator it = factory_map_.find(scheme);
   if (it == factory_map_.end()) {
     handler->reset();
     return ERR_UNSUPPORTED_AUTH_SCHEME;