Make CertVerifier a pure virtual interface.

net/http/http_network_transaction_unittest.cc

Index: net/http/http_network_transaction_unittest.cc
diff --git a/net/http/http_network_transaction_unittest.cc b/net/http/http_network_transaction_unittest.cc
index 124f64269fad6791d653812dfb605977b02a4dd3..877aa93956938d0b3e50152186c491a1c3bb2e40 100644
--- a/net/http/http_network_transaction_unittest.cc
+++ b/net/http/http_network_transaction_unittest.cc
@@ -22,6 +22,7 @@
 #include "net/base/completion_callback.h"
 #include "net/base/host_cache.h"
 #include "net/base/mock_host_resolver.h"
+#include "net/base/multi_threaded_cert_verifier.h"
 #include "net/base/net_log.h"
 #include "net/base/net_log_unittest.h"
 #include "net/base/request_priority.h"
@@ -108,7 +109,7 @@ struct SessionDependencies {
   // Default set of dependencies -- "null" proxy service.
   SessionDependencies()
       : host_resolver(new MockHostResolver),
-        cert_verifier(new CertVerifier),
+        cert_verifier(new MultiThreadedCertVerifier),
         proxy_service(ProxyService::CreateDirect()),
         ssl_config_service(new SSLConfigServiceDefaults),
         http_auth_handler_factory(
@@ -118,7 +119,7 @@ struct SessionDependencies {
   // Custom proxy service dependency.
   explicit SessionDependencies(ProxyService* proxy_service)
       : host_resolver(new MockHostResolver),
-        cert_verifier(new CertVerifier),
+        cert_verifier(new MultiThreadedCertVerifier),
         proxy_service(proxy_service),
         ssl_config_service(new SSLConfigServiceDefaults),
         http_auth_handler_factory(