Revert of Convert //net and //chromecast to std::unordered_*

net/http/http_response_headers.h

Index: net/http/http_response_headers.h
diff --git a/net/http/http_response_headers.h b/net/http/http_response_headers.h
index 4d2bcc06464d56da3326d90ea18354741dfb46fd..a3126aa72d76c45fa1bc9e69fdec9bab0bf72470 100644
--- a/net/http/http_response_headers.h
+++ b/net/http/http_response_headers.h
@@ -9,9 +9,9 @@
 #include <stdint.h>
 
 #include <string>
-#include <unordered_set>
 #include <vector>
 
+#include "base/containers/hash_tables.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string_piece.h"
@@ -323,7 +323,7 @@
  private:
   friend class base::RefCountedThreadSafe<HttpResponseHeaders>;
 
-  using HeaderSet = std::unordered_set<std::string>;
+  typedef base::hash_set<std::string> HeaderSet;
 
   // The members of this structure point into raw_headers_.
   struct ParsedHeader;