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

net/base/priority_queue.h

Index: net/base/priority_queue.h
diff --git a/net/base/priority_queue.h b/net/base/priority_queue.h
index 037faed86b201db0e89618655aeb67a87d9431f0..f60b88c69a05319958ae80eb97db603cda350484 100644
--- a/net/base/priority_queue.h
+++ b/net/base/priority_queue.h
@@ -47,7 +47,11 @@ class PriorityQueue : public base::NonThreadSafe {
   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; }
 
@@ -64,6 +68,10 @@ class PriorityQueue : public base::NonThreadSafe {
       return (priority_ == other.priority_) && (iterator_ == other.iterator_);
     }
 
+    void Reset() {
+      *this = Pointer();
+    }
+
    private:
     friend class PriorityQueue;