Add a mechanism to disable IPv6....

net/base/mock_host_resolver.h

Index: net/base/mock_host_resolver.h
===================================================================
--- net/base/mock_host_resolver.h	(revision 29420)
+++ net/base/mock_host_resolver.h	(working copy)
@@ -121,7 +121,9 @@
   void AddSimulatedFailure(const std::string& host);
 
   // HostResolverProc methods:
-  virtual int Resolve(const std::string& host, AddressList* addrlist);
+  virtual int Resolve(const std::string& host,
+                      AddressFamily address_family,
+                      AddressList* addrlist);
 
  private:
   struct Rule;
@@ -141,9 +143,11 @@
   }
 
   // HostResolverProc methods:
-  virtual int Resolve(const std::string& host, AddressList* addrlist) {
+  virtual int Resolve(const std::string& host,
+                      AddressFamily address_family,
+                      AddressList* addrlist) {
     event_.Wait();
-    return ResolveUsingPrevious(host, addrlist);
+    return ResolveUsingPrevious(host, address_family, addrlist);
   }
 
   base::WaitableEvent event_;