Remove HttpAuth::Scheme enum in favor of a string.

net/http/http_auth_controller.h

Index: net/http/http_auth_controller.h
diff --git a/net/http/http_auth_controller.h b/net/http/http_auth_controller.h
index efcab5e88e0d8a83eb58a940af1116187182046a..e61b4854227cd1ff2d55c70fbb11c7ea44fd27a4 100644
--- a/net/http/http_auth_controller.h
+++ b/net/http/http_auth_controller.h
@@ -69,8 +69,8 @@ class NET_EXPORT_PRIVATE HttpAuthController
 
   virtual scoped_refptr<AuthChallengeInfo> auth_info();
 
-  virtual bool IsAuthSchemeDisabled(HttpAuth::Scheme scheme) const;
-  virtual void DisableAuthScheme(HttpAuth::Scheme scheme);
+  virtual bool IsAuthSchemeDisabled(const std::string& scheme) const;
+  virtual void DisableAuthScheme(const std::string& scheme);
 
  private:
   // Actions for InvalidateCurrentHandler()
@@ -160,7 +160,7 @@ class NET_EXPORT_PRIVATE HttpAuthController
   HttpAuthCache* const http_auth_cache_;
   HttpAuthHandlerFactory* const http_auth_handler_factory_;
 
-  std::set<HttpAuth::Scheme> disabled_schemes_;
+  std::set<std::string> disabled_schemes_;
 
   CompletionCallback callback_;
 };