Change HostResolver::Resolve() to take an std::unique_ptr<Request>* rather than a RequestHandle*

net/dns/mapped_host_resolver.h

Index: net/dns/mapped_host_resolver.h
diff --git a/net/dns/mapped_host_resolver.h b/net/dns/mapped_host_resolver.h
index 20c249f7b096047bc8337daffb930b79064415af..6ef004d68bd8f4f9adbf51da412af05b4980a075 100644
--- a/net/dns/mapped_host_resolver.h
+++ b/net/dns/mapped_host_resolver.h
@@ -49,12 +49,11 @@ class NET_EXPORT MappedHostResolver : public HostResolver {
               RequestPriority priority,
               AddressList* addresses,
               const CompletionCallback& callback,
-              RequestHandle* out_req,
+              std::unique_ptr<Request>* out_req,
               const BoundNetLog& net_log) override;
   int ResolveFromCache(const RequestInfo& info,
                        AddressList* addresses,
                        const BoundNetLog& net_log) override;
-  void CancelRequest(RequestHandle req) override;
   void SetDnsClientEnabled(bool enabled) override;
   HostCache* GetHostCache() override;
   std::unique_ptr<base::Value> GetDnsConfigAsValue() const override;