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

Relanded with a fix to TestDownloadRequestHandler.

> Do //chromecast at the same time as //net since there aren't many
> uses in //chromecast and one needs to be changed to mirror a //net
> API change.
>
> Review URL: https://codereview.chromium.org/1869503003
>
> Cr-Commit-Position: refs/heads/master@{#386485}

[email protected],[email protected]
BUG=576864,554287

Review URL: https://codereview.chromium.org/1897033002

Cr-Commit-Position: refs/heads/master@{#388545}
diff --git a/net/base/network_interfaces_linux.h b/net/base/network_interfaces_linux.h
index a030608b..8fe2284 100644
--- a/net/base/network_interfaces_linux.h
+++ b/net/base/network_interfaces_linux.h
@@ -9,8 +9,8 @@
 // of network_interfaces_linux.cc to address_tracker_linux and tests.
 
 #include <string>
+#include <unordered_set>
 
-#include "base/containers/hash_tables.h"
 #include "net/base/address_tracker_linux.h"
 #include "net/base/network_interfaces.h"
 
@@ -24,7 +24,7 @@
 NET_EXPORT bool GetNetworkListImpl(
     NetworkInterfaceList* networks,
     int policy,
-    const base::hash_set<int>& online_links,
+    const std::unordered_set<int>& online_links,
     const internal::AddressTrackerLinux::AddressMap& address_map,
     GetInterfaceNameFunction get_interface_name);