HostResolver supports optional CNAME lookups.

net/base/host_resolver_proc.h

 // Copyright (c) 2010 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_HOST_RESOLVER_PROC_H_
 #define NET_BASE_HOST_RESOLVER_PROC_H_
 
 #include <string>
 
 #include "base/ref_counted.h"
@@ skipping 12 matching lines @@
 // the HostResolver implementation using them can be multi-threaded.
 class HostResolverProc : public base::RefCountedThreadSafe<HostResolverProc> {
  public:
   explicit HostResolverProc(HostResolverProc* previous);
 
   // Resolves |host| to an address list, restricting the results to addresses
   // in |address_family|. If successful returns OK and fills |addrlist| with
   // a list of socket addresses. Otherwise returns a network error code.
   virtual int Resolve(const std::string& host,
                       AddressFamily address_family,
+                      HostResolverFlags host_resolver_flags,
                       AddressList* addrlist) = 0;
 
  protected:
   friend class base::RefCountedThreadSafe<HostResolverProc>;
 
   virtual ~HostResolverProc() {}
 
   // Asks the fallback procedure (if set) to do the resolve.
   int ResolveUsingPrevious(const std::string& host,
                            AddressFamily address_family,
+                           HostResolverFlags host_resolver_flags,
                            AddressList* addrlist);
 
  private:
   friend class HostResolverImpl;
   friend class MockHostResolverBase;
   friend class ScopedDefaultHostResolverProc;
 
   // Sets the previous procedure in the chain.  Aborts if this would result in a
   // cycle.
   void SetPreviousProc(HostResolverProc* proc);
@@ skipping 18 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(HostResolverProc);
 };
 
 // Resolves |host| to an address list, using the system's default host resolver.
 // (i.e. this calls out to getaddrinfo()). If successful returns OK and fills
 // |addrlist| with a list of socket addresses. Otherwise returns a
 // network error code.
 int SystemHostResolverProc(const std::string& host,
                            AddressFamily address_family,
+                           HostResolverFlags host_resolver_flags,
                            AddressList* addrlist);
 
 }  // namespace net
 
 #endif  // NET_BASE_HOST_RESOLVER_PROC_H_