Reland '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 17833a47258290b5398a2418453358ab5ceed727..653eacc4d44e30b86d15c41532ec2514ef8ba435 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"
@@ -324,7 +324,7 @@ class NET_EXPORT HttpResponseHeaders
  private:
   friend class base::RefCountedThreadSafe<HttpResponseHeaders>;
 
-  typedef base::hash_set<std::string> HeaderSet;
+  using HeaderSet = std::unordered_set<std::string>;
 
   // The members of this structure point into raw_headers_.
   struct ParsedHeader;