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

net/disk_cache/memory/mem_entry_impl.h

Index: net/disk_cache/memory/mem_entry_impl.h
diff --git a/net/disk_cache/memory/mem_entry_impl.h b/net/disk_cache/memory/mem_entry_impl.h
index bcb25c8639a22d135afa757399451751016924b6..11634e6ab9a883a64856f31d5e459b65707eb36f 100644
--- a/net/disk_cache/memory/mem_entry_impl.h
+++ b/net/disk_cache/memory/mem_entry_impl.h
@@ -8,9 +8,9 @@
 #include <stdint.h>
 
 #include <string>
-#include <unordered_map>
 #include <vector>
 
+#include "base/containers/hash_tables.h"
 #include "base/containers/linked_list.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
@@ -133,7 +133,7 @@
                MemEntryImpl* parent,
                net::NetLog* net_log);
 
-  using EntryMap = std::unordered_map<int, MemEntryImpl*>;
+  typedef base::hash_map<int, MemEntryImpl*> EntryMap;
 
   static const int kNumStreams = 3;