DNS: Support reprioritization of requests.

net/dns/host_resolver_mojo.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/dns/host_resolver_mojo.h"
 
 #include <utility>
 
 #include "mojo/public/cpp/bindings/binding.h"
 #include "net/base/address_list.h"
@@ skipping 74 matching lines @@
 }
 
 int HostResolverMojo::ResolveFromCache(const RequestInfo& info,
                                        AddressList* addresses,
                                        const BoundNetLog& source_net_log) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(1) << "ResolveFromCache " << info.host_port_pair().ToString();
   return ResolveFromCacheInternal(info, CacheKeyForRequest(info), addresses);
 }
 
+void HostResolverMojo::ChangeRequestPriority(RequestHandle req,
+                                             RequestPriority priority) {
+  // Do nothing, since Resolve() discarded the priority anyway.

[Randy Smith (Not in Mondays), 2016/04/28 18:04:40]

Oh, for goodness sake.  What uses the DNS resolver through the mojo interface? 
(This is not a blocking comment on this CL, I'm just a bit miffed at mojoization
tossing priority.)

[Julia Tuttle, 2016/05/04 14:43:20]

No idea!

[mmenke, 2016/05/04 17:33:16]

The out of process PAC stuff, I would assume.  I believe the PAC code has always
tossed priority, so this most likely inherited the behavior from that.

Could be completely wrong about all that, though.

[Randy Smith (Not in Mondays), 2016/05/05 00:07:25]

Matt's probably right.  Willing to put a TODO in the Mojo code near the
declaration of Resolve() to *not* drop priority on the floor?  If it's not
needed for the current use case, that's fine, but I don't want someone else
starting to rely on that implementation and not realize they don't get priority.

[Julia Tuttle, 2016/05/05 12:47:56]

I put a note in the .h instead, where I think a user might be more likely to see
it.

[mmenke, 2016/05/05 12:51:12]

I think there's actually a bug filed against the proxy to correctly send the
priorities, too...Anyhow, agree that this interface should support it, too.

+}
+
 void HostResolverMojo::CancelRequest(RequestHandle req) {
   DCHECK(thread_checker_.CalledOnValidThread());
   // Deleting the Job closes the HostResolverRequestClient connection,
   // signalling cancellation of the request.
   delete static_cast<Job*>(req);
 }
 
 HostCache* HostResolverMojo::GetHostCache() {
   return host_cache_.get();
 }
@@ skipping 41 matching lines @@
   }
   callback_.Run(error);
   delete this;
 }
 
 void HostResolverMojo::Job::OnConnectionError() {
   ReportResult(ERR_FAILED, interfaces::AddressListPtr());
 }
 
 }  // namespace net