DNS: Support reprioritization of requests.

net/dns/host_resolver_impl.cc

Index: net/dns/host_resolver_impl.cc
diff --git a/net/dns/host_resolver_impl.cc b/net/dns/host_resolver_impl.cc
index a224b8c4e38a87d943fef29f7494c738186e1096..5559c8d460fbbed748f66146ac784f2d8e1cf9d7 100644
--- a/net/dns/host_resolver_impl.cc
+++ b/net/dns/host_resolver_impl.cc
@@ -574,6 +574,7 @@ class HostResolverImpl::Request {
   }
 
   RequestPriority priority() const { return priority_; }
+  void set_priority(RequestPriority priority) { priority_ = priority; }
 
   base::TimeTicks request_time() const { return request_time_; }
 
@@ -583,8 +584,7 @@ class HostResolverImpl::Request {
   // The request info that started the request.
   const RequestInfo info_;
 
-  // TODO(akalin): Support reprioritization.
-  const RequestPriority priority_;
+  RequestPriority priority_;
 
   // The resolve job that this request is dependent on.
   Job* job_;
@@ -1367,6 +1367,16 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job,
     UpdatePriority();
   }
 
+  void ChangeRequestPriority(Request* req, RequestPriority priority) {
+    DCHECK_EQ(key_.hostname, req->info().hostname());
+    DCHECK(!req->was_canceled());
+
+    priority_tracker_.Remove(req->priority());
+    req->set_priority(priority);
+    priority_tracker_.Add(req->priority());
+    UpdatePriority();
+  }
+
   // Marks |req| as cancelled. If it was the last active Request, also finishes
   // this Job, marking it as cancelled, and deletes it.
   void CancelRequest(Request* req) {
@@ -1474,6 +1484,12 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job,
     DCHECK_EQ(1u, num_occupied_job_slots_);
   }
 
+  AddressList MakeAddressListForRequest(const AddressList& list) const {
+    if (requests_.empty())
+      return list;
+    return AddressList::CopyWithPort(list, requests_.front()->info().port());
+  }
+
   void UpdatePriority() {
     if (is_queued()) {
       if (priority() != static_cast<RequestPriority>(handle_.priority()))
@@ -1482,12 +1498,6 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job,
     }
   }
 
-  AddressList MakeAddressListForRequest(const AddressList& list) const {
-    if (requests_.empty())
-      return list;
-    return AddressList::CopyWithPort(list, requests_.front()->info().port());
-  }
-
   // PriorityDispatch::Job:
   void Start() override {
     DCHECK_LE(num_occupied_job_slots_, 1u);
@@ -2045,6 +2055,16 @@ int HostResolverImpl::ResolveFromCache(const RequestInfo& info,
   return rv;
 }
 
+void HostResolverImpl::ChangeRequestPriority(RequestHandle req_handle,
+                                             RequestPriority priority) {
+  DCHECK(CalledOnValidThread());
+  Request* req = reinterpret_cast<Request*>(req_handle);
+  DCHECK(req);
+  Job* job = req->job();
+  DCHECK(job);
+  job->ChangeRequestPriority(req, priority);
+}
+
 void HostResolverImpl::CancelRequest(RequestHandle req_handle) {
   DCHECK(CalledOnValidThread());
   Request* req = reinterpret_cast<Request*>(req_handle);