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

net/dns/host_resolver_mojo.h

Index: net/dns/host_resolver_mojo.h
diff --git a/net/dns/host_resolver_mojo.h b/net/dns/host_resolver_mojo.h
index 08519d2fc420bc10ad4df7c2680ee2c12456217b..35732bc21f9558749c0ac74114c2e12f042cc162 100644
--- a/net/dns/host_resolver_mojo.h
+++ b/net/dns/host_resolver_mojo.h
@@ -37,18 +37,16 @@ class HostResolverMojo : public HostResolver {
               RequestPriority priority,
               AddressList* addresses,
               const CompletionCallback& callback,
-              RequestHandle* request_handle,
+              std::unique_ptr<Request>* request,
               const BoundNetLog& source_net_log) override;
   int ResolveFromCache(const RequestInfo& info,
                        AddressList* addresses,
                        const BoundNetLog& source_net_log) override;
-  void ChangeRequestPriority(RequestHandle req,
-                             RequestPriority priority) override;
-  void CancelRequest(RequestHandle req) override;
   HostCache* GetHostCache() override;
 
  private:
   class Job;
+  class RequestImpl;
 
   int ResolveFromCacheInternal(const RequestInfo& info,
                                const HostCache::Key& key,