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

net/disk_cache/simple/simple_index.cc

Index: net/disk_cache/simple/simple_index.cc
diff --git a/net/disk_cache/simple/simple_index.cc b/net/disk_cache/simple/simple_index.cc
index a8be3ac4badee1cb75c955b1a3eebb6fbaa7ecee..f6ccd3eb1dd7547449915738f5a8b66c9d19e7f1 100644
--- a/net/disk_cache/simple/simple_index.cc
+++ b/net/disk_cache/simple/simple_index.cc
@@ -401,8 +401,7 @@
 
   EntrySet* index_file_entries = &load_result->entries;
 
-  for (std::unordered_set<uint64_t>::const_iterator it =
-           removed_entries_.begin();
+  for (base::hash_set<uint64_t>::const_iterator it = removed_entries_.begin();
        it != removed_entries_.end(); ++it) {
     index_file_entries->erase(*it);
   }