[net/dns] Perform A/AAAA queries for AF_UNSPEC resolutions in parallel.

net/base/prioritized_dispatcher.cc

 // Copyright (c) 2012 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/base/prioritized_dispatcher.h"
 
 #include "base/logging.h"
 
 namespace net {
 
@@ skipping 27 matching lines @@
   DCHECK(job);
   DCHECK_LT(priority, num_priorities());
   if (num_running_jobs_ < max_running_jobs_[priority]) {
     ++num_running_jobs_;
     job->Start();
     return Handle();
   }
   return queue_.Insert(job, priority);
 }
 
+PrioritizedDispatcher::Handle PrioritizedDispatcher::AddAtHead(
+    Job* job, Priority priority) {
+  DCHECK(job);
+  DCHECK_LT(priority, num_priorities());
+  if (num_running_jobs_ < max_running_jobs_[priority]) {
+    ++num_running_jobs_;
+    job->Start();
+    return Handle();
+  }
+  return queue_.InsertAtFront(job, priority);
+}
+
 void PrioritizedDispatcher::Cancel(const Handle& handle) {
   queue_.Erase(handle);
 }
 
 PrioritizedDispatcher::Job* PrioritizedDispatcher::EvictOldestLowest() {
   Handle handle = queue_.FirstMin();
   if (handle.is_null())
     return NULL;
   Job* job = handle.value();
   Cancel(handle);
@@ skipping 34 matching lines @@
   if (num_running_jobs_ >= max_running_jobs_[job_priority])
     return false;
   Job* job = handle.value();
   queue_.Erase(handle);
   ++num_running_jobs_;
   job->Start();
   return true;
 }
 
 }  // namespace net