HostResolver supports optional CNAME lookups.

net/base/mock_host_resolver.h

Index: net/base/mock_host_resolver.h
diff --git a/net/base/mock_host_resolver.h b/net/base/mock_host_resolver.h
index d08dc42cb20fe993d0aab4de4ce8f44f229f4026..5a1df7f716b78bd46d8298b7a5b8ecfdac3e10de 100644
--- a/net/base/mock_host_resolver.h
+++ b/net/base/mock_host_resolver.h
@@ -128,6 +128,7 @@ class RuleBasedHostResolverProc : public HostResolverProc {
   // HostResolverProc methods:
   virtual int Resolve(const std::string& host,
                       AddressFamily address_family,
+                      HostResolverFlags host_resolver_flags,
                       AddressList* addrlist);
 
  private:
@@ -152,9 +153,11 @@ class WaitingHostResolverProc : public HostResolverProc {
   // HostResolverProc methods:
   virtual int Resolve(const std::string& host,
                       AddressFamily address_family,
+                      HostResolverFlags host_resolver_flags,
                       AddressList* addrlist) {
     event_.Wait();
-    return ResolveUsingPrevious(host, address_family, addrlist);
+    return ResolveUsingPrevious(host, address_family, host_resolver_flags,
+                                addrlist);
   }
 
  private: