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

net/http/http_auth_cache.cc

Index: net/http/http_auth_cache.cc
diff --git a/net/http/http_auth_cache.cc b/net/http/http_auth_cache.cc
index 2cc2c0ce556249576f52b298efe7536753b1bca1..43ce7d660bf14c5105717edb4e94c5cfdd733cdc 100644
--- a/net/http/http_auth_cache.cc
+++ b/net/http/http_auth_cache.cc
@@ -68,7 +68,7 @@ HttpAuthCache::~HttpAuthCache() {
 // Performance: O(n), where n is the number of realm entries.
 HttpAuthCache::Entry* HttpAuthCache::Lookup(const GURL& origin,
                                             const std::string& realm,
-                                            HttpAuth::Scheme scheme) {
+                                            const std::string& scheme) {
   CheckOriginIsValid(origin);
 
   // Linear scan through the realm entries.
@@ -110,7 +110,7 @@ HttpAuthCache::Entry* HttpAuthCache::LookupByPath(const GURL& origin,
 
 HttpAuthCache::Entry* HttpAuthCache::Add(const GURL& origin,
                                          const std::string& realm,
-                                         HttpAuth::Scheme scheme,
+                                         const std::string& scheme,
                                          const std::string& auth_challenge,
                                          const AuthCredentials& credentials,
                                          const std::string& path) {
@@ -154,8 +154,7 @@ void HttpAuthCache::Entry::UpdateStaleChallenge(
 }
 
 HttpAuthCache::Entry::Entry()
-    : scheme_(HttpAuth::AUTH_SCHEME_MAX),
-      nonce_count_(0) {
+    : nonce_count_(0) {
 }
 
 void HttpAuthCache::Entry::AddPath(const std::string& path) {
@@ -196,7 +195,7 @@ bool HttpAuthCache::Entry::HasEnclosingPath(const std::string& dir,
 
 bool HttpAuthCache::Remove(const GURL& origin,
                            const std::string& realm,
-                           HttpAuth::Scheme scheme,
+                           const std::string& scheme,
                            const AuthCredentials& credentials) {
   for (EntryList::iterator it = entries_.begin(); it != entries_.end(); ++it) {
     if (it->origin() == origin && it->realm() == realm &&
@@ -213,7 +212,7 @@ bool HttpAuthCache::Remove(const GURL& origin,
 
 bool HttpAuthCache::UpdateStaleChallenge(const GURL& origin,
                                          const std::string& realm,
-                                         HttpAuth::Scheme scheme,
+                                         const std::string& scheme,
                                          const std::string& auth_challenge) {
   HttpAuthCache::Entry* entry = Lookup(origin, realm, scheme);
   if (!entry)