reapply r70628. It was wrongly blamed for breaking Linux valgrind bots.

net/proxy/proxy_script_fetcher_impl_unittest.cc

 // 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.
 
 #include "net/proxy/proxy_script_fetcher_impl.h"
 
 #include <string>
 
 #include "base/file_path.h"
 #include "base/compiler_specific.h"
@@ skipping 29 matching lines @@
         net::CreateSystemHostResolver(net::HostResolver::kDefaultParallelism,
                                       NULL, NULL);
     cert_verifier_ = new net::CertVerifier;
     proxy_service_ = net::ProxyService::CreateFixed(no_proxy);
     ssl_config_service_ = new net::SSLConfigServiceDefaults;
 
     http_transaction_factory_ = new net::HttpCache(
         net::HttpNetworkLayer::CreateFactory(host_resolver_, cert_verifier_,
             NULL, NULL, NULL, proxy_service_, ssl_config_service_, NULL, NULL,
             NULL),
+        NULL,
         net::HttpCache::DefaultBackend::InMemory(0));
   }
 
  private:
   ~RequestContext() {
     delete http_transaction_factory_;
     delete cert_verifier_;
     delete host_resolver_;
   }
 };
@@ skipping 265 matching lines @@
     string16 text;
     TestCompletionCallback callback;
     int result = pac_fetcher.Fetch(url, &text, &callback);
     EXPECT_EQ(ERR_IO_PENDING, result);
     EXPECT_EQ(OK, callback.WaitForResult());
     EXPECT_EQ(ASCIIToUTF16("This was encoded as UTF-16BE.\n"), text);
   }
 }
 
 }  // namespace net