Add more unit tests for net/base/host_resolver.

net/base/host_resolver.h

 // Copyright (c) 2006-2008 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_H_
 #define NET_BASE_HOST_RESOLVER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 39 matching lines @@
 
  private:
   class Request;
   friend class Request;
   scoped_refptr<Request> request_;
   DISALLOW_COPY_AND_ASSIGN(HostResolver);
 };
 
 // A helper class used in unit tests to alter hostname mappings.  See
 // SetHostMapper for details.
-class HostMapper {
+class HostMapper : public base::RefCountedThreadSafe<HostMapper> {
  public:
   virtual ~HostMapper() {}
   virtual std::string Map(const std::string& host) = 0;
+
+ protected:
+  // Ask previous host mapper (if set) for mapping of given host.
+  std::string MapUsingPrevious(const std::string& host);
+
+ private:
+  friend class ScopedHostMapper;
+
+  // Set mapper to ask when this mapper doesn't want to modify the result.
+  void set_previous_mapper(HostMapper* mapper) {
+    previous_mapper_ = mapper;
+  }
+
+  scoped_refptr<HostMapper> previous_mapper_;
 };
 
 #ifdef UNIT_TEST
 // This function is designed to allow unit tests to override the behavior of
 // HostResolver.  For example, a HostMapper instance can force all hostnames
 // to map to a fixed IP address such as 127.0.0.1.
 //
 // The previously set HostMapper (or NULL if there was none) is returned.
 //
 // NOTE: This function is not thread-safe, so take care to only call this
 // function while there are no outstanding HostResolver instances.
 //
 // NOTE: In most cases, you should use ScopedHostMapper instead, which is
 // defined in host_resolver_unittest.h
 //
 HostMapper* SetHostMapper(HostMapper* host_mapper);
 #endif
 
 }  // namespace net
 
 #endif  // NET_BASE_HOST_RESOLVER_H_