DNS: Support reprioritization of requests.

net/dns/host_resolver.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_DNS_HOST_RESOLVER_H_
 #define NET_DNS_HOST_RESOLVER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 145 matching lines @@
                       const BoundNetLog& net_log) = 0;
 
   // Resolves the given hostname (or IP address literal) out of cache or HOSTS
   // file (if enabled) only. This is guaranteed to complete synchronously.
   // This acts like |Resolve()| if the hostname is IP literal, or cached value
   // or HOSTS entry exists. Otherwise, ERR_DNS_CACHE_MISS is returned.
   virtual int ResolveFromCache(const RequestInfo& info,
                                AddressList* addresses,
                                const BoundNetLog& net_log) = 0;
 
+  // Changes the priority of the specified request. |req| is the handle returned
+  // by Resolve(). ChangeRequestPriority must NOT be called after the request's
+  // completion callback has already run or the request was canceled.
+  virtual void ChangeRequestPriority(RequestHandle req,
+                                     RequestPriority priority);
+
   // Cancels the specified request. |req| is the handle returned by Resolve().
   // After a request is canceled, its completion callback will not be called.
   // CancelRequest must NOT be called after the request's completion callback
   // has already run or the request was canceled.
   virtual void CancelRequest(RequestHandle req) = 0;
 
   // Enable or disable the built-in asynchronous DnsClient.
   virtual void SetDnsClientEnabled(bool enabled);
 
   // Returns the HostResolverCache |this| uses, or NULL if there isn't one.
@@ skipping 17 matching lines @@
  protected:
   HostResolver();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(HostResolver);
 };
 
 }  // namespace net
 
 #endif  // NET_DNS_HOST_RESOLVER_H_