Reland 'Convert //net and //chromecast to std::unordered_*'

net/http/http_response_headers.cc

Index: net/http/http_response_headers.cc
diff --git a/net/http/http_response_headers.cc b/net/http/http_response_headers.cc
index edaf9225ac38df21af44aebb799aee47277af3c3..aa0fdd1815c98273daff2157e5d090d4bca2a12f 100644
--- a/net/http/http_response_headers.cc
+++ b/net/http/http_response_headers.cc
@@ -10,6 +10,7 @@
 #include "net/http/http_response_headers.h"
 
 #include <algorithm>
+#include <unordered_map>
 #include <utility>
 
 #include "base/format_macros.h"
@@ -457,7 +458,7 @@ void HttpResponseHeaders::GetNormalizedHeaders(std::string* output) const {
   // be a web app, we cannot be certain of the semantics of commas despite the
   // fact that RFC 2616 says that they should be regarded as value separators.
   //
-  typedef base::hash_map<std::string, size_t> HeadersMap;
+  using HeadersMap = std::unordered_map<std::string, size_t>;
   HeadersMap headers_map;
   HeadersMap::iterator iter = headers_map.end();