Cleanup: Use AUTH_SCHEME enum instead of a string.

net/http/http_auth_handler.cc

Index: net/http/http_auth_handler.cc
===================================================================
--- net/http/http_auth_handler.cc	(revision 70740)
+++ net/http/http_auth_handler.cc	(working copy)
@@ -12,7 +12,7 @@
 namespace net {
 
 HttpAuthHandler::HttpAuthHandler()
-    : auth_scheme_(AUTH_SCHEME_MAX),
+    : auth_scheme_(HttpAuth::AUTH_SCHEME_MAX),
       score_(-1),
       target_(HttpAuth::AUTH_NONE),
       properties_(-1),
@@ -41,10 +41,9 @@
 
   // Init() is expected to set the scheme, realm, score, and properties.  The
   // realm may be empty.
-  DCHECK(!ok || !scheme().empty());
   DCHECK(!ok || score_ != -1);
   DCHECK(!ok || properties_ != -1);
-  DCHECK(!ok || auth_scheme_ != AUTH_SCHEME_MAX);
+  DCHECK(!ok || auth_scheme_ != HttpAuth::AUTH_SCHEME_MAX);
 
   return ok;
 }