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

net/dns/dns_hosts.h

Index: net/dns/dns_hosts.h
diff --git a/net/dns/dns_hosts.h b/net/dns/dns_hosts.h
index e55772b7e35f95913f13f7b9f9cf0523d508a57e..2ce7c52dc16fb5e2eb80835a3b6aea3d506bbeac 100644
--- a/net/dns/dns_hosts.h
+++ b/net/dns/dns_hosts.h
@@ -9,25 +9,31 @@
 
 #include <map>
 #include <string>
-#include <unordered_map>
 #include <utility>
 #include <vector>
 
+#include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
-#include "base/strings/string_piece.h"
 #include "net/base/address_family.h"
 #include "net/base/ip_address.h"
 #include "net/base/net_export.h"
 
 namespace net {
+  typedef std::pair<std::string, AddressFamily> DnsHostsKey;
+};
 
-using DnsHostsKey = std::pair<std::string, AddressFamily>;
+namespace BASE_HASH_NAMESPACE {
 
-struct DnsHostsKeyHash {
-  std::size_t operator()(const DnsHostsKey& key) const {
+template<>
+struct hash<net::DnsHostsKey> {
+  std::size_t operator()(const net::DnsHostsKey& key) const {
     return base::StringPieceHash()(key.first) + key.second;
   }
 };
+
+}  // namespace BASE_HASH_NAMESPACE
+
+namespace net {
 
 // There are OS-specific variations in how commas in the hosts file behave.
 enum ParseHostsCommaMode {
@@ -50,7 +56,13 @@
 // 127.0.0.1 localhost
 // 10.0.0.1 localhost
 // The expected resolution of localhost is 127.0.0.1.
-using DnsHosts = std::unordered_map<DnsHostsKey, IPAddress, DnsHostsKeyHash>;
+#if !defined(OS_ANDROID)
+typedef base::hash_map<DnsHostsKey, IPAddress> DnsHosts;
+#else
+// Android's hash_map doesn't support ==, so fall back to map.  (Chromium on
+// Android doesn't use the built-in DNS resolver anyway, so it's irrelevant.)
+typedef std::map<DnsHostsKey, IPAddress> DnsHosts;
+#endif
 
 // Parses |contents| (as read from /etc/hosts or equivalent) and stores results
 // in |dns_hosts|. Invalid lines are ignored (as in most implementations).