AddressInfo: Include <memory> for std::unique_ptr

IWYU. This fixes the libstdc++ build after commit 135dadb4 ("Encapsulate
addrinfo in RAII type"):

In file included from ../../net/dns/address_info.cc:5:
../../net/dns/address_info.h:56:12: error: no template named 'unique_ptr' in namespace 'std'
      std::unique_ptr<AddrInfoGetter> getter = nullptr);
      ~~~~~^
../../net/dns/address_info.h:73:34: error: no template named 'unique_ptr' in namespace 'std'
  AddressInfo(addrinfo* ai, std::unique_ptr<AddrInfoGetter> getter);
                            ~~~~~^
../../net/dns/address_info.h:77:8: error: no template named 'unique_ptr' in namespace 'std'
  std::unique_ptr<AddrInfoGetter> getter_;
  ~~~~~^

Bug: 957519
Change-Id: I81f3403ad4b0aee6dc815241b41814d528b867ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1894000
Auto-Submit: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Commit-Queue: Eric Orth <ericorth@chromium.org>
Reviewed-by: Eric Orth <ericorth@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711773}

net/dns/address_info.h

@@ -5,6 +5,7 @@
 #ifndef NET_DNS_ADDRESS_INFO_H_
 #define NET_DNS_ADDRESS_INFO_H_
 
+#include <memory>
 #include <string>
 #include <tuple>