[net] HostResolverImpl + DnsTransaction + DnsConfigService = Asynchronous DNS ready for experiments.

net/base/priority_queue.h

 // 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.
 
 #ifndef NET_BASE_PRIORITY_QUEUE_H_
 #define NET_BASE_PRIORITY_QUEUE_H_
 #pragma once
 
 #include <list>
 #include <vector>
@@ skipping 29 matching lines @@
 #endif
 
  public:
   typedef uint32 Priority;
 
   // A pointer to a value stored in the queue. The pointer becomes invalid
   // when the queue is destroyed or cleared, or the value is erased.
   class Pointer {
    public:
     // Constructs a null pointer.
-    Pointer() : priority_(kNullPriority) {}
+    Pointer() : priority_(kNullPriority) {
+#if !defined(NDEBUG)
+      id_ = static_cast<size_t>(-1);
+#endif
+    }
 
     bool is_null() const { return priority_ == kNullPriority; }
 
     Priority priority() const { return priority_; }
 
 #if !defined(NDEBUG)
     const T& value() const { return iterator_->second; }
 #else
     const T& value() const { return *iterator_; }
 #endif
 
     // Comparing to Pointer from a different PriorityQueue is undefined.
     bool Equals(const Pointer& other) const {
       return (priority_ == other.priority_) && (iterator_ == other.iterator_);
     }
 
+    void Reset() {
+      *this = Pointer();
+    }
+
    private:
     friend class PriorityQueue;
 
     // Note that we need iterator not const_iterator to pass to List::erase.
     // When C++0x comes, this could be changed to const_iterator and const could
     // be added to First, Last, and OldestLowest.
     typedef typename PriorityQueue::List::iterator ListIterator;
 
     static const Priority kNullPriority = static_cast<Priority>(-1);
 
@@ skipping 128 matching lines @@
 #endif
 
   ListVector lists_;
   size_t size_;
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_PRIORITY_QUEUE_H_