Disable the TLS version fallback.

components/ssl_config/ssl_config_service_manager_pref_unittest.cc

 // Copyright (c) 2012 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 "components/ssl_config/ssl_config_service_manager.h"
 
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/values.h"
@@ skipping 155 matching lines @@
           &local_state, base::ThreadTaskRunnerHandle::Get()));
   ASSERT_TRUE(config_manager.get());
   scoped_refptr<SSLConfigService> config_service(config_manager->Get());
   ASSERT_TRUE(config_service.get());
 
   SSLConfig ssl_config;
   config_service->GetSSLConfig(&ssl_config);
   // The command-line option must not have been honored.
   EXPECT_LE(net::SSL_PROTOCOL_VERSION_TLS1, ssl_config.version_min);
 }
+
+// Tests that fallback beyond TLS 1.0 cannot be re-enabled.

[Ryan Sleevi, 2016/02/09 07:22:29]

And if they force a field trial via --force-fieldtrial?

+TEST_F(SSLConfigServiceManagerPrefTest, NoTLS1Fallback) {
+  scoped_refptr<TestingPrefStore> local_state_store(new TestingPrefStore());
+
+  TestingPrefServiceSimple local_state;
+  local_state.SetUserPref(ssl_config::prefs::kSSLVersionFallbackMin,
+                          new base::StringValue("tls1"));
+  SSLConfigServiceManager::RegisterPrefs(local_state.registry());
+
+  scoped_ptr<SSLConfigServiceManager> config_manager(
+      SSLConfigServiceManager::CreateDefaultManager(
+          &local_state, base::ThreadTaskRunnerHandle::Get()));
+  ASSERT_TRUE(config_manager.get());
+  scoped_refptr<SSLConfigService> config_service(config_manager->Get());
+  ASSERT_TRUE(config_service.get());
+
+  SSLConfig ssl_config;
+  config_service->GetSSLConfig(&ssl_config);
+  // The command-line option must not have been honored.
+  EXPECT_EQ(net::SSL_PROTOCOL_VERSION_TLS1_2, ssl_config.version_fallback_min);
+}